Make a club in Manager mode with the maximum budget. Create fifteen or sixteen players with maximum attributes. Set their birthday to 1990 so they are very young. Build only as many players to have only the minimum for your squad to be ready for your created team. You will then have an invincible team in Career mode. If you do not have many players you will not have to pay plenty of money to them. Try giving them as low of an amount of money as you can to accept.