Here's a few I can give you since I can't see your steam account. note: none of these games can be redeemed on steam it's buy and ship.
amazon sell BG1 and BG2 with the expansions for like $15 last time I checked. best to start by playing the game to be honest. BG1 can be fairly punishing at times but it is really fun and immersive. if you want to buy digitally because you can't wait. You can buy from http://www.gog.com/ but it is a little more expensive
There's a 4 in 1 boxset of the original (Non EE version) of 1, and 2.
As far as finding it on GoG though, I'm not sure.