How many players you will be able to buy and sell next season will depend on how many tokens you have and in-game cash.
I would offload: Jung, Fricke, Strobl,Szabo The next players on the out list are your 2 penalty-kick takers, Lee and Donno
When new season starts, try to sign 5*GK, 5*DC, 5*DR, 5*DL, 5*MC, 5*ST, Basically a 5* player in each of the positions, you should be able to get middle-aged, mid-rating 26-28 quality players on the transfer market for a few tokens each if your limited token-wise, If you have 50-100 tokens spare you try your hand trying to sign a few of the younger players.