Your squad is the foundation of your club. You can have a maximum of 26 players, starting off with a maximum of 22. The other four slots can be gained for example by earning specific achievements or they can be bought during special promotions. The better your squad, the better the chance to win titles, like your league championship.
Always make sure that your team is well-balanced, to receive full efficiency in your training. On the positions defence, midfield,on the wings and in the offence, you should`t have no more than seven players, or the training efficiency goes down. For the goalkeepers it is limited to three players without losing efficiency.