Questing
The easiest way to level is to simply complete quests to get Sword of the New World Vis . The best questing strategy is to accept every quest from an area, complete as many as you can, turn them all in at once, then repeat until you have completed all the quests that you can from that area before moving onto the next area. If a quest is too hard don't be afraid to skip it completely or save it for later.

Instances
Instances can be fun and can provide good loot to Sword of the New World Vis players who do them, but they are not required content for leveling. Instances will help you learn your role in a group setting and how to play well with other classes. Usually in an instance your most important role is providing crowd control through polymorph, then damage, then buffs and food/water. All these roles are important however and if you neglect any of them you are not fulfilling your role as a mage in an instance.

Grinding
Grinding alone is not the most efficient way to level a mage, or any class. Grinding is when you simply kill mobs in an area over and over again in order to level. As you might imagine this can become very boring very quickly.

Good mobs to grind for mages, single target or AoE, are melee mobs that have no ranged attacks, abilities that affect spell casting speed, or abilities that can prevent you from kiting snw vis, like knock down.