Sorry long post incoming, but you asked for advise so i am gonna give it based on my experiences of being here for just over a year, 60% ROI in that time shows that i must be doing something right.
To be fair i think that you have the right idea kinda in building yourself a base of players with a good potential to win divs, I do believe that's the way to build a successful port.
Personally if it were me there are a quite a few players that you have which i would get shot off ASAP, then i would use then recycle this money onto the players that you want to earn you divs then go from there.
I know that you wont want to hear this but for me Gnabry would be first on the chopping block. The guys price is built on sand (2 freak performances over an entire season, yeah if he does it again his price might explode, but is that rise really worth it for the rest if the time as money slowly drips out of him as more and more people lose the faith) Next on the block would be Jesus, again massively overrated in my book . Dybala there is a definite argument to keep him, but for me he is another one that blows hot and cold so his price goes up and down accordingly, which is fine as long as you realize whats going on and don't panic sell. Rashford is a keeper for me, truth is that any of the big utd players are good holds for the long term, And don't listen to the shit that people saying about him on this thread e.g sell Rashy because he is competing with Bruno what a crock of shit that is, Rashford is a fwd Bruno is a mid i.e. they compete in different dividend pools so NOT in direct competition if anything an on form Bruno helps Rashford with all the assists that he is going to give him. I mean if you follow that logic then no one would ever buy another forward other then Messi cause Messi is the best PB performer out there so in effect Messi is the one providing the competition not just for Rashford but literally every fwd on the index. As far as the greenwood situation goes, i think you have called it right Mason will get bleed into the team slowly, Ok so he has played well last couple of games and will start the next and he is a good player excellent PB base for one so young. There is a lot of short term FOMO going on with him at the moment, to be fair i am weighing up getting some more of him myself (because the fact that i only have 10 shares in him is criminal nice 3.89 buying price so i got a bit of profit tied up in him to eat up), but long term i think at this stage you have to assume that Sancho will come in next season, so this will limit game time for greenwood i.e. he will form part of the rotation system in the front 3, so i think there may well be an opportunity to get on at a cheaper price then now, if you want to wait.
I think out of you port i would keep the following and get shot of the rest (reasons below)
Neymar/Pogba/Rashy/Dybala(but he needs to start producing or he will be next on the block)/Jota/Zaniolo/Goretzka/Halstenburg/ if you fancy a punt on a non PB player then Szoboslai is probably one of the best out there for that atm so i would buy some more of him just to sit on for 18 months/tah i would keep as he can come good/Aouchiche yeah keep him as part of your youth trend player, but i think its at least 18 months to 2 years before he starts returning regular wins up to you if you want to hold that long with little returns, but has the rep and the pedigree so will always pick up CA over that time.
Thauvin i think if he was ever going to do anything he would have done by now that fact that Marseile and has been for a while tells you all you need to know. Kulusevski best case scenario for him is that he gets loaned out probably to a 2nd rate Serie A team worst case scenario he just ends up buried under the mountain of midfielders at Juve and he doesn't get game time, either way its not great Coman liable to break at any given moment and now increased competition from sane who is at least 3 times the player Coman is, for me that's a definite get rid but i know that's an unpopular opinion. Piatek, urm there might be an argument to keep until next season see how he goes but to me he looks like a one season wonder but unfortunately that one season was 2 years ago. Gies and Gonzalez I must admit i don't know who these guys are, my bad, but i do know a fair bit about football so the fact that i don't know them means that other people might not know them either, hence why they don't go up in price (prices up until when full OB come in are nothing more then a popularity contest the bigger profile as a player you have then the more people buy the higher the price goes, similarly players with next to no profile just stagnate or go down) Golovin is a good PB player he can win you divs but monaco have not been a good team for a few years and mid table obscurity is never good for anyone's price, so yeah keep if you want but not for me. Laimer to be honest i looked at him a while ago i thought he was value, but after watching pretty much all of RBLs games this year, i think that he doesn't get forward enough and doesn't get enough goals to every really trouble the top of PB rankings, and for me there is also a massive ? about RBL in general next season a lot will depend on how they replace/adapt to not having Werner anymore it could go either way imo, you have the same problem with Sabitzer and to be fair i have the same issue and i am undecided whether to keep for next season. if you want some additional cover in the RBL midfield i would suggest Kevin Kampl as an alternative to Laimer, he just seems to have a bit more about him more goal involvement and more likely-hood of winning but even that is a stretch as there are better players in the RBL team. B Silva quality player but playing pep roulette every week and serious competition from KDB i think holds back his price, but i don't think he is a terrible hold so that's a sell if you have had enough or a keep if you still have the faith no wrong answers on this just go with your gut. Kleindiest I think you either need to keep for at least another year (unless he gets transfer spec then sell on the rise which is now all you have left on this bet) or you cut your losses and just put it down to a punt that didn't come off, to me you might as well keep but up to you.
I think you list of possible new buys for your port is generally good (other then the the players mentioned above) For the next year or so i think TAA is a must so glad you have identified that. (need to get some in myself or next season)
As for index trends, the honest truth here is that you cant be blamed for no knowing when you first start everyone gets tripped up by this, it takes time to identify understand them, but now that you have been here for a while you should have a better idea of them. For me the way i handle this is through diversification. You have been around along enough now to know what the main trends are e.g you got your div earners trend, your youth trend, the PB to MB switch trend as the season goes into summer, then there is your mid season January transfer spec trend, to name a few there are probably more. But to deal with this its pointless trying to predict when each one as it happens (all that does is stress you out and by the time that you realize whats going on its too late and it just costs you time and commission which is not what you want) So what you do is you rebuild your port (with the money that you have got with the duds you just sold) with these trends in mind. Honestly get a pen and paper go through each trend and make a list of players that fit into each one, factor in whatever other parameters you want and then whittle your list down and try to have at least 3 or 4 players for each trend. The point is that you have a foot in each camp so it does not matter which trend we are currently going though as you will always have some players that will benefit from it, so one part of your port goes down cause its off trend, but another part of it goes up cause its on trend. okay you might not always have the biggest riser but you will always have some risers to offset any losses.
When you are re building your port try and build it more evenly i think that half you problem is that you went to big to quickly on Certian players eg Gnabry so when it all went to shit you were so over exposed to that one player that it dragged down the rest of your port because you have nothing to compensate those losses so try and build steadily and don't allow any one part of your port to take over the rest (if you want to have a lopsided port ok then fair enough but over extend on the div earning part of your port because at least they chip in regular payments to offset any falls in price). This is my pie chart of percentage of portfolio costs this nice smooth even approach has done well for me and i think it can do well for you too.
When you buy your players its always good to think about teams as well as the players themselves, Use what you know e.g. Bayern/PSG are pretty much unstoppable in the german/French leagues and that isn't gonna change anytime soon Bonified fact!! So there is no harm in going in heavy and covering a few positions, i quite like doing both full backs, 1 or 2 central/attacking mid and 1/2 of the striking positions. Reason being is that if a team smashes it on one week e.g. bayern win 6 - 0 or something then chances are you will win def PB with the CS bonus and maybe a goal or assist but most of the assist are probably coming from midfield but that's fine cause you have 2 positions covered and a score like that there is a decent chance that someone has hit a hatty so yours odds on for fwd PB, but even if a team do have a really good game there is always one guy that does nothing, so by covering multiple positions you improve your chances of winning PB divs over multiple positions on the same day and you reduce your chances of holding the player that doesn't do well, or even if you do hold them, you probably also hold the players that did really well so no harm done. So in this example if you had bought into Pavard / Davies / Kimmeich/ Lewandowski at the beginning of the season then you would be pretty happy about now, far happier then if you had just bought Gnabry or just Coman or just lewa. So think of some teams that you think have a 75% + chance of getting in to UCL positions next season and then back them, Germans are the easiest to do this with i think its pretty likely it will be Bayern/Dortmond/RBl then either
leverkussen or gladbach, in spain its Barca/Real/Seville then either Athleti / Sociadad, in France PSG/Lyon (if they shape up and dont sell everyone)/Rennes/Lille even the EPL is getting easier to read LPL/City/Utd/Chelsea . In italy its JUVE/Inter looks like Lazio have joined the party this year maybe Atalanta. So the point is that you already know which teams are going to be fighting it out so go a back the players in those teams, rather then trying to find the surprise package team/player that comes from nowhere, that shit is hard to predict and will most likely fail. You can still be selective tho, eg at the beginning of the season (few weeks in lazio started to look good like they were gonna do something but on assessing the team it turn out that they only have 3 decent PB players Luis Alberto/Immobile/SMS (maybe Acerbi depending on what sort of age profile you want) so just cover those 3 positions and you cant go wrong. Another way would be to take atalanta for example watching them this season you see that they cant defend for shit, so if you want to cover them you cover the attack and forget the defense, a good all round team e.g. Seville you can spread it about a bit more to reflect that their players can return divs in all 3 positions.
Last point your 3 spaces that you have for short term trading, yeah its a good idea to have short term strategy but again rather then allocating specific spots in you port for this, better just to keep a permanent cash balance, then jump on an opportunity when one comes around, keep it flexible. Trying to nail down who the short term risers will be is pointless it wont work because you cant predict the unpredictable ( I don't because i just don't have the spare cash to keep a cash balance permanently but i do believe that this is the way to do it if you want to go down that road).
hopefully i have not come across all condescending apologies if i have i am not trying to be, but at the same time i don't want to sugar coat it either, at the end of the day your port value is what it is for a reason and whilst if you wait long enough it will most likely come good in the end, i do believe that you could benefit from a restructuring if not a full re build.