Re: Day hiker interested in camping, where to start?

The various resources people have already suggested sound good. In my opinion, though, since you plan on going camping with a group, the first place to start would be with them. That way you can get a sense for how *they* camp, and what kind of gear they use. You don't want to go spending money on things you don't need (for example the group might use large tents with room for an extra person, so why buy your own tent). The same could be true of cookware and other items. And in any case it would be helpful to know what they use so you get similar equipment so you'll be comparably equipped when you go with the group.

Once you know this, then you can go to REI or the other resources mentioned armed with a little background knowledge.