People have already suggested some good and reasonably accessible bags. Two more I would recommend for the very beginning of your Norrathian adventures:
Tailored Large Bag and Tailored Large Belt Pouch. You might have to farm up some spiderling silk. I bet you can easily find someone with 40+ Tailoring to make these for you.
Though they are only 6 slots, the bags themselves weigh 0.6 or 0.8 TC (Tom Cruises), allowing you to carry heavier items (but fewer).
I believe in carrying a variety of bags: some light and small, some heavier but better (Bag of Sewn Evil Eye). Heavy loot goes in weight reduction bags, light loot goes in cheap bags.