Oh man, you don't have a clue about training process =]
This guide will be the best to begin with: https://forum.topeleven.com/tutorial...s-players.html
A lot of the info from there is outdated, but I strongly recommend you to start with this one. It is not about training, but about... well, everything.
Regarding your question, every position has its own best drills, because drills train different skills. And there is no universal recipe, no magic pill. But all the drills have the same efficiency (experience divided by condition) if they are the same level, so they all increase the overall quality at an equal pace.