Many managers suggest to train 1v1 forward for first two seasons beacause this training is the more complete in BB .
So if you decide to train 1v1Forward you will need 6 players, and you should buy player with low OD/ID and high HN and IS to enjoy elastic effect when HN and IS will go up.
If you want train 3 position you should buy players with balanced skills, 5 at least in every skill (18 yo) but these players have a high price.
It would better a 19yo with balanced skills , 5/6 at least that is less expensive.