To me, stamina is far less important than magicka and health. You can completely ignore it and be fine. If your only magical skill is going to be Illusion then I'd take 2 health to every 1 magicka. However, in order to cast Calm, you do need more than 100 magicka. So you may want to build that up first, getting it up to 200 or so, and taking a couple of perks that'll reduce your costs. But after that, go with mostly health.
I personally find the poisons in the game to be incredibly weak, with the exception of paralysis potions. Slow is okay and the rest just don't seem to do much at all. I once tried to poison Narfi during a DB quest with a supposedly powerful poison and it only took about 2/3 of his health. A real letdown.
But, I suppose if your alchemy is 100 and you have the poisoner perk, it may do better.
I'd also suggest smithing so that you can improve your DB and TG armor. Granted you have to get to 60 in order to get the perk to improve enchanted stuff, but it's so worth it. It really svcks to have a level 35 character with an armor rating that can't stand up to a steel arrow fired from an Orcish bow.
Enchanting is always good too, but if you're going to strictly stick with DB or TG armor then it's largely uneccessary. You won't be able to enchant weapons worth a crap but with a high smithing score you can create strong enough weapons anyway; and you don't have to go around buying/finding soul gems and chasing down every creature in Tamriel just so you can keep your badass Glass Bow of Nuclear Destruction charged up.