Well it would depend on what team are you gonna use and how much budget you have to spend...
But... I'll toss in a few names though.
DM-> Felix Horn Myhre (Ullern), Kristoffer Ajer (Start/Celtic). The first one starts at a really modest Norwegian team (3rd tier) and can be bought be a measly 5,5 k, while the second (unless you updated your game and have him at the Celtic) you can move him out of Norway by least than a million.
LM/RM-> Dennis Praet (Anderlecht). He's not a world class, but he's young and he can play in almost every area of the midfield (everywhere but Defensive Midfielder), if you're patient you can get him on a free since his contract runs out at the end of the second season.
ST-> Sergio Díaz (Cerro Porteño/Real Madrid Castilla), Richairo Zivkovic (Ajax). If you've updated your game to have this summer's transfers done... forget about him since Real Madrid will not let him go no matter what... If not you can obtain one of the best strikers in the game potential wise for less than 3 millions. For Zivkovic you must have to wait a year before going after him since he's on loan at the start of the game, but you can get him for a sum between 5 and 8 millions at the start ot the second season and for a prospect like him... is one **** of a bargain.
That's pretty much it for the time being, I'll drop some more names if I can come up with something useful.