To start your career with any team, at the main menu, select "Team Management" > "Edit Player". Choose any team and begin to edit their players up to a rating of 78. You can leave some players with an overall rating of 83, but try to keep most players at a rating of 78. You can edit almost all, if not all, of your team's players, After that, go to Career mode and your team should be available. Also because your overall rating is 78, your players will not ask for a higher salary and you can always keep that team, unlike just swapping the starting eleven's for the subs (even if you can choose that team, you will lose a lot of salary and eventually be fired). Do not worry about your players having an overall rating of 78. If you keep winning, your players will almost go back to their original overall stats. Also, go to "Club Transfers" and take some players you do not need or like. This will also make your players ask for less salary, because you will have less players.
Unlock the following teams by performing the corresponding tasks:
TEAM - HOW TO UNLOCK All-African team - Win the World Cup with an African team. All-Americans team - Win the World Cup with a North or South American team. All-Asian team - Win the World Cup with an Asian team. All-European team - Win the World Cup with an European team. All-World team - Unlock the All-African, All-Americans, All-Asian, and All-European all-star teams.