Sort your players by quality and check the ones with lowest quality, lets say the lowest 3 ones.
Sort again by age, the eldest ones with lowest quality from above chart might have to be sold. -(a good age for selling is above 30 at your lvl)-
Dont overdo with selling, i would not suggest more than 3 players leaving club for the first season because game is still fresh to you.

whatever you decide, sell any or none, see what you got left with and plan for next season respectively.... if you got many MC's go for a 3-5-2 formation for example.... your priority is to fit your players in a formation that suits you the best !

good luck with your decisions my friend