Hello mate, my suggestion is a real training.
Buy 2,3 players with 18, 19 years (with potential 6 or more), get a coach at least lvl 5 and begin to train them.
On that way you can develop your team, be stronger, or you can get money for them later.
Stamina is not an so good option when you don't have quality players and you can't get the value of the player bigger with that training. If you need some help feel free to contact me.
Cheers!
This is where we hold them!