Well, some gear will grant you additional mana regen rate and some gear will grant you a skill that has the same effect as a manarune. Ultimately though, managing our mana is a bit part of the game so find a safe place and rest until it refills.
I've never needed 2 manasurge runes, but that being said I haven't played every class. During the early and mid-game, fights will usually be over fairly quickly so you might not even need manasurge, but having one is handy. In the later game, you should get mana regen items and talents, and/or get high spell crit chance and get items that give mana when firing a critical spell. If you play Archmage, get the Disruption Shield talent at level 12 and use it as soon as you get below 25% mana.
- Rest after and before every fight
- manasurge rune
- if you use highcost mana spells: give Willpower some love.
- Disruption shield as an archmage solves everything.