Go to Edit mode and increase all of the abilities of the players that you want to select for your team. After this, go to Master League mode and chose the option "Create Custom Team". Edit everything desired until you get to the default players list. Select every one of the default players individually, and change them to the players that you edited before. You will start the league with a very low budget, but your team's budget will become stable after you win many matches. It will be easier to do this because your team now has perfect abilities.
