Im planning on painting my dads 96 Rav4 glossy black using a single stage paint. There are some parts that require body filler such as the front of the due because it has a lot of small rich dings from driving. I dont want to use both epoxy and filler primer because i dont have too much money to get both. Can i just but bondo to the areas that need bondo and just use a filler (urethane) primer over the exiting original primer sand that down to make it nice and even then use the single stage paint? Any suggestions would be nice since this will be my first paint job.

Sure, as long as one of the following are true:

1. you are not down to metal
2. or, your 2K primer is rated as direct-to-metal (DTM) capable.

Over the last two years I think I've used epoxy primer once and that was to test out the brand I sell here.