I'm interested in multiboxing for gathering. I've never multiboxed before and I have a couple of questions

Should I multibox on a bunch of different bnet accounts, or should I just use different licences all on 1 bnet account?

Also, when multibox gathering professions, do all of my characters have to be on the same server or will them being on different servers cause wonkiness? I was thinking of spreading out across multiple servers so I don't flood the market with a bunch of supplies.

Thanks!