Alchemy... definitely alchemy. Sad thing about alchemy is, it's needed for most poison / evil based builds and as i mentioned in a private correspondence once, there's nothing evil about plucking daisies.
That said, i have also more than once mentioned that levelling enchanting naturally will allow one to craft poisons and potions without hoarding too many ingridents, if you know what to look for.
Basic stuff like wheat and blue mountain flowers, which can be found throughout the holds will allow for a decent restore potion. Same logic goes for the restore magicka potions. Lingering damage poisons made from the common ingredients from the marsh areas is another, though in reality, with the dragonborn DLC, it's better to make weakness to poisons concoctions as compared to making the poison itself.
The only other poison as a magic user i can see would be of benefit to say the least would be the weakness to magic or weakness to (x) element, for getting more oomph out of the spells.
I dislike Enchanting in most cases except where it is implemented in a way to emphasise character or used as a replacement for other skills like Twisted's and Ben's Stalhrim Master.
In all other cases I find it to be an empty pursuit in which the goal is more important than the journey. By the time the goal is reached the journey is already over.
Gameplay or roleplay?
For gameplay I absolutely hate Enchanting, just because it's such a chore to level and it's so repetitive. Fortify Sneak, ring, soul gem. Fortify sneak, ring, soul gem. Rinse and repeat. So boring.
Roleplay-wise, though, I don't like the idea of making loads of Dwarven Bows just so I can make an Orcish Shield. Shouldn't I as an Orc already know that?