Everyone gets into the sport differently. Here's what worked for me:
Took a roll lesson in a pool: $30
Decided I'd give it a go and bought out an ex-boater's gear: $300
Old Dagger river runner
(Just ask around, I bet that one out of 10 households in Denver have a full set of whitewater gear collecting dust)
I paddled around Union Chutes and on lakes to practice my roll. Swam lots. Got many good tips, encouragement and gear retrieval from experienced boaters.
The I met some boaters roughly at my entry skill level. Started to get on rivers: Foxton and Deckers. Swam lots. Nailed a few combat rolls. Gained confidence. Ran more rivers with more people...got hooked.
Check out this site, perfect for your needs: Kayaking Information
I say, buy a full set of used gear cheap. If you like the sport, you'll upgrade your gear and sell the used gear for roughly what you paid for it. If you don't like the sport, you can use your PFD to hunt for those damn lost golf balls.