Welcome aboard! I should've been riding for at least the last 10 years--but it's a grim future in which one is lamenting the past.

If you can go light often enough, you might think about a smallish hydration-type pack. Most days I only need to carry clean shirt, socks, and underwear (along with basic odds and ends). For the last week or so, I've been using a Camelbak Blowfish. It's a neat little size that rides nicely and isn't big enough for a heavy load. I think it's become my pack of choice for when I don't have to drag along more stuff. The options are many, though...