New Redemption Grab Bag now includes an assortment of 500 cards from five (5) different expansion sets. Available at Cactus website.
Since some packs have different sizes, it depends on which packs you're using. You want to give people enough to make a legal deck, which requires at least 50 cards, and at the same time try to give at least a little wiggle room. I think generally you want to use at least 6 packs (per person).
This is great, thanks! What's the best way to go about supplying the draft?