Pots have 2 min CD, so if you use them at about 70% of your mana, the CD will be over at about 50%, so you take another 1,
mages also have evocation, so they get +60% mana with 8 min CD, and than the conjured stuff gives them mana as well with a 2min CD (not shared with potions), and ofc your gear with MP5 or mana regain when crit.
:)