Do I need an individual or a team subscription?
You can automate your whole team with an individual account provided that one person sets up and maintains all the rules, and that the triggers for the rules end in "by anyone", e.g. when a card is moved to "Done" by anyone.
This person's Trello user will effectively be the one performing the automations: it will look as if this person was the one performing the automated actions, regardless of who performed the action that triggered the rule. All the command runs will be accrued to the rule creator.
Buttons, on the other hand, are limited to one per person in free accounts: each person can create a button, and buttons can be shared, but each free user will only see one button (the one they created, or one shared one if they didn't create one.)
If a paid account creates multiple buttons and shares them, free accounts will still only see one.
A team account allows everyone to create multiple rules and buttons, and has a weekly quota pooled across all users. As you add more people to the team, the shared team quota increases.