After collecting enough cards, mix your starting team with the extra players.
Choose formations and assign the correct role to the players that are best
in those tasks. Get chemistry bonuses by placing players with the same
nationality together as often as possible. When you cannot fill a position
optimally, try to place a player whose statistics best fits that area until
you find someone better suited.
You can use the Transfer Market to get the players needed for your team.
Also use it to eliminate players you no longer require.