1) You shouldn't buy so many young players, you won't have enough greens to train them.
10-11 should be your max young players (ft)

2)
Should I train them or wait for having stronger training level and search for FT at the beggining of the next season?
Training levels are going really slowly.
You need months to reach some descent levels (3 whistles).
Play your game, do your training, forget about this.

3)
it is better to train first skills or SA?
Always first the sa/new position and then skills.
Read my summary.

4) Your money and tokens are really bad.
For the first, I suggest to stay level this season.
For money, find friends and play a lot of friendlies.
Check the tickets price (in friendlies is much less - about your LV price or lower).