How much you spend will really depend on how much you want to spend for it. When I get my LO's printed, I spend about $30 or so, but those are for at least 20 12x12 pages. I get them printed professionally. I don't print them myself.
Re: kits, like nuance mentioned, there are a lot of freebies out there. You may want to try those out first as you explore the world of digi. There are a lot of free downloads right here at SBB too. SBB also has a free newsletter that you can subscribe to. A lot of the other sites have newsletters too that offer discount codes or feature new products their designers are coming out with. SBB has a lot of awesome designers in the store so I'd suggest browsing the store.
I suggest setting a budget for yourself first coz it'll be so easy to get carried away with all the gorgeous goodies available!

LOL!