So, I'm in my second season with Real Madrid.
In the first season, I loaned most of the youngsters, no need to make any sale.
At the start of the second season, I have decided to sell Casilla, Benzema, Pepe, Silva, and many youngster who were not as promising (on stats). I decided to buy Auba, Courtois, Aaron Martin (Espanyol), and Ghoulam since (I think) those are the positions that need subs and they were all related to RM at some point.
Having sold Benzema, I decided to keep the system puting Ronaldo up front and Aubameyang on the wing, since he's got what's need and has also played there and that way I could put Bale on the left wing.
I usually play two system, either 4-3-3 (Real's formation), fixed the way you see in the diagram, or a 4-4-2 with Auba and Ronaldo as ST and moving James or Isco to the right wing or putting Morata as an ST and Auba on the wing.
The roster consists of:
GK: Thibaut Courtois who rotates with Navas. I usually give some time to Yañez on some matches. 
I'm planning to sell Navas, maybe next season and recall Alexandro Marco from loan. In a few seasons, I might try buying Donnarumma since I don't see him leaving Milan in a while or maybe not at all. I'm also tempted to go for Arrizabalaga or Rico (this one's the most difficult since, in real life, Sevilla wouldn't sell him).
DEFENSE: Marcelo, Ramos, Varane, Carvajal.
I decided to sell Pepe (age) since I got Diego, Nacho (will probably sell), Vallejo, and kept Lienhart (planning to sell too). On LB, I decided to sell Fabio and bought Ghoulam and Aaron to slowly replace Marccelo (he gets a lot of injuries in my CM too). Sent Tejero on loan.
On RB I got Carvajal, Danilo rotates with him but I'm planning to sell him since it's what's most like gonna happen IRL. Hakimi is quite good IG and Nacho plays well there too. Next season I'll get an RB after selling Danilo.
MIDFIELD: Kroos, Modric rotating with Marcos (will send him on loan), Kovacic, and Casemiro. Febas is on loan along with Torro.
CAM: James/Isco rotating with Asensio. Decided to send Odegaard on loan again. Since there's rumors of either James or Isco leaving, I might try buying Dele Alli since there's rumors on him or buy Dybala and try him on CAM.
WINGS: Bale and Auba, rotating with Vazquez and sometimes Cristiano. I decided to keep Enzo and send him on loan since I doubt Zidane will sell his own son (for now).
ST: Cristiano/Morata. When Morata is upfront Cristiano plays on the wings. Kept Mariano and Mayoral but sent them on loan.
Next season, I will probably sell Ronaldo and buy Dybala, puting Auba as ST and Dybala on the wing. I don't know if Bernardo Silva (Monaco) is quite realistic for now since I've got too many people on the attack side and they might want to leave if not played as much. I also don't know if selling Morata is a good idea since I've heard rumors of him wanting to leave. Yet, if I do, I would probably go for Andre Silva (Porto) since he's been related to the team and he might want to take a step forward in his career.
What do you think? Comment about what you think and who might be missing in from my shortlist.