It's not uncommon to see someone who's looking for a cheap (or free) alternative to Adobe Lightroom, and I saw another one of these threads this morning. I'm normally all about trying out cheaper alternatives, but not in this case.
I started years ago with Paint.net (free) and some old image editor I can't remember at the moment. I bought Corel's Paint Shop Pro on sale for $60 or so, which was a huge step up, but eventually I wanted to get my hands on Adobe's RAW converter and bought Photoshop Elements -- again, at $60 or so, I believe. A few months later, Adobe sent me an offer to get LR for $99, and I snapped that up.
Had I to do it all over again, I'd try to find a deal on LR right off the bat and skip everything else until you're ready to buy more software. Lightroom + PS-E is a great combo, but since I got LR, I use PS-E for maybe 1% of the photos I do any editing on at all (not counting the ones I reject out-of-hand).
The thing that makes LR different from all those other options is its killer workflow. Lots of people will point out that you can do almost everything LR does in Paint.net or Gimp (is it still "The Gimp"?) or whatever. This is true, but it's going to take you gobs more time -- especially compared to your productivity once you get good at LR. If you've got lots of extra time that you don't want to use for, say, taking photographs, then there's absolutely no reason for you to go out and buy LR.
Save for LR, and watch for it to go on sale, then pick it up. I've seen several LR deals over the last year or so that put LR at $100-150, which is an absolute no-brainer, or it's available for around that if you're a student, too.