Event Types control many aspects of your events, including how they are categorized for budget purposes.

To review and update these settings, please go to Site Configuration → Event Types.  Update an event type to see how it is categorized for the budget.

Scroll down to the "Financial" section, you see where you can designate the budget type.

This is really only relevant for events that allow monetary transactions.

The default value is "Activity", which is anything other than a fundraiser.  This is the proper setting for campouts and other outings.

Select "Fundraiser" for any event type which is going to raise money for the group.