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.
For clean sheets to be credited in season, tournament, Be A Pro Season, manager modes (everything outside exhibitions), it would be the final keeper present at the end of a shutout (clean sheet) game. For instance, if you start with Edwin Van der Sar in the first half, Thomasz Kusczak in the beginning of second half, but finish with Wayne Rooney in goal because Kusczak was red-carded, and the final score was 2-0, Rooney will be credited with the clean sheet, and not Edwin Vander Sar. Kusczak is ineligible because he was red-carded. The clean sheet is void if any goals are scored against them. If any keeper conceded a goal, any substitute keepers in goal will not benefit even if they didn't concede any further goals.
If your player is injured and is out forseveral days, you can speed up his recovery. Use the player as a sub while he is injured. He will suffer another less serious injury, and should heal in about a week or less.
Have the transfer window open. For example, if playing as Manchester United, put Tevez on the transfer market. Negotiate for someone like Eto'o, who is better. If you get him, something will appear if someone bid for Tevez. Let Tevez go as you have got Eto'o. Instead of paying all that money for him, you are only losing a little bit.
Have the transfer window open and search for good free agent players with at least skill level 75 and below the age of 30. The more skills with younger age, the better. Sign them and offer them the highest wage you can. If your negotiator skills are low, the player you try to sign will reject your offer. Try re-signing him with a higher offer. For example, if the player wage is $35,000 the first time, the board will only allow you $45,000 for the player. The player will reject any offer below $70,000. When you re-sign him for the second time, the board will allow you more than $80,000. You can now sign him. When the player is yours, change his status to "For Sale". Bigger clubs will be interested in him and you can get a lot of money. If you manage a small club with a limited budget, do not keep this player. Otherwise, you will not have enough money for other players.
-In Manager mode you will have a 90+ overall team. The Youth Academy in your office will have youth players of about 70 at the age of 15 or 16. You can either keep playing with them or sell them in your fourth of fifth season to earn millions of dollars. Try this with J. Baxter, Rodwell, Bunce, Morris, etc.