Chromis will work well for a budget. I started with 1, then decided to start a small school and added 2 more to have a group of 3. They did well for quite a while so I recently added 4 more to have a school of 7. They do school well, and definitely look good in my reef.
I'd avoid even numbers of any schooling fish, especially chromis, since they will get aggressive towards one another if kept in even groupings. In fact, I've heard that the magic numbers are 3, 7, and any odd number more than 7. HTH.