Hi Tammy, These days most themes work with BuddyPress, although there can be occasional inconsistencies.
In general there are two types of themes, general themes not written specifically for BuddyPress these are typically free. There are also BP specific themes, often for a cost and written specifically with BP in mind.
Personally I use general themes and add the custom features I want. In the majority of cases you don’t actually need to do much customisation to get the site feel that you desire.
So really the decision is about the specific visual attributes of the theme as they apply to the site you want to create and for that only you know what you are looking for.