I want to know about making really strong poisons to be honest? any advice?
First there is the obvious: increase Alchemy Skill by making a whole lot of potions and poisons. And get the best Alchemy equipment you can.
Particular at low levels getting ingredients can be the problem. Since most foods Restore Fatigue making restore Fatigue potions to self train Alchemy is a good way to get better. Some people "steal" food from farms around Skingrad (I don't with most characters, even though it's not considered stealing by the game). Also there is a huge amount of flax around Skingrad, and it weighs nothing. So if you can use that as an ingredient it helps alot. Also a bunch of nice ingredients south of Bravil.
For equipment, Mages Guildhalls sell them. And you can find them in dungeons, often better than what is sold. Conjurer Dungeons are best, followed by Necromancer. Undead, Mythic Creature and Vampire dungeons may also have some.
BUT the real secret to powerful potions and poisons is multiple effects. Adding a bunch of damage to a single poison is powerful. Or maybe add invisibily, restore health and restore fatigue to one potion, then use it when you're surrounded by tough enemies. Or fortify Health and Strength if your character is a warrior in a tough fight.
And think beyond Restore Health and Damage Health. For example, Lilly Nectar, Primrose, Motherworth and Lady Smock are all readily available. And mixing them at Expert level creates a damage fatigue and damage strength potion. That is very very powerful against enemy warlords (NPC or Goblin). Also Damage Speed is an amazing poison, particularly against enemies without a ranged attack.
I like this website for figuring out muliteffect potions and poisons
http://oblivion.melian.cc/?cmd=cmdOblivionAlchemyWizard
Any other questions on Alchemy?