I prefer 10's for chain casting.
Stam30's are even better. NPC buyable and it won't drain your int.
What are you talking even talking about?
Who cares if stams are sold by NPCs, they don't restore mana, which is what we're drinking the potions for.
And draining int? Potions don't drain int. None of them do, not even MP30s. They can cause potion poisoning however, but if you're getting yourself poisoned on purpose, you're not using int anyway.