My priest, Athelas, has maxed out alchemy and I was wondering what to specialize in. I'm interested in what would help out the guild more than making money. Any suggestions?

If you check out the Wiki and it says at the top who specializes in what.

My two cents: Potions is useless. Beam got potions, but ya just don't make that many potions for it to be useful. And the return isn't that great. Think about it, one extra health potion vs. one extra elixir (or flask) vs. one extra transmute.

That said, I think potions is probably the cheapest to get (just gotta put together a Bot run). You could get that, then pay 150G to switch to one of the others.