Have shot before but now looking to get a rifle of my own?

I'm looking for suggestions on a rifle which would best suit my needs. I've never really shopped around for guns before because until now I didn't really care, I'll shoot what ever my grandfather hands me. I've shot rifles on about a dozen different occasions over the last 5 or so years. I've shot a couple different 22 cal, a 308, and an 8mm before. I've shot only a few hundred rounds in my life. Nothing that I've tried seemed to be too over powering. I'm looking for a smaller caliber riffle some where between the 22 and 308. The 22 seams like the logical choice because of the price of ammo and because most would say it is the best gun to learn on. I'm also considering something a little bigger because I might want to hunt medium sized game next year. For now the gun would be used strictly for perfecting my aim. In the fall if I feel comfortable with my shooting ability I might hunt small game like squires or rabbits. I would like to be all set up with everything I would need for under $500. What rifles should I consider?