Go check out Emmerald's site, it has a list of the best gear for tanking, including which is easiest obtained, the best investment, etc. www.emmerald.net.
If you link to your armory some of the experts here can make recommendations.
Also, yes, do BGs for gear. The S2 shoulders and arguably head are better than anything else out there pre-raid, ditto the belt and bracers. Check Emmerald's, you'll see the dungeons you should farm (relatively few). And work on Cenarion Rep for Earthwarden, it's worth it.
Edited, Aug 14th 2008 1:51pm by tuskerdu