In Edit mode, increase all of the abilities of the players that you want for your team. After this, go to Master League mode and select the option "Create Custom Team". Edit everything desired until you get to the default players list, then choose 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.