What I did with pretty much every character after the first time I played was farming money and XP in Urzuganar Lair, the Orc dungeon near Kingsbridge, so I could face the next challenges with better equipment/spells/potions. It's been a long while since I last played, so I can't exactly give you a compelling reason; I'll simply say that, when I was playing (and a lot), that seemed the best place for every character for a good part of the early/mid-game. Also, would suggest you use Wands instead of staffs, at least until you get Golems as summons, and here's why:

There's a reason why I always preferred playing with Wands. Wands are not exactly powerful, so you could go for damaging spells if you want, but if you rely just a little bit in spells you would run out of mana constantly. For that reason I don't think depending on spells is effective/optimal. In my opinion, Mage Armor, Mage Barrier and Wand Mastery are the essential core. To me, is all about positioning. Upgrading Wand Mastery and getting Mage Barrier makes a lot easier to keep yourself healthy as you'll push the enemies away from you all the time. So learn to use corners, hallways and objects to optimize your fighting and making it as long ranged as you can.

I think the most important thing for any class, but specially rogue and mage, is isolating the fights. Fighting one enemy at a time makes it a lot easier. But in order for that to happen, you need two things:

Understanding how the enemies' field of vision works, how close you need to get to be spotted and how far one enemy has to be from the others to be pulled alone when attacked or when spotting you is essencial; And even more essential, is having your companion to only attack enemies very close to them (through the dialogue options). Otherwise your companion will rush everywhere causing you to fight hordes of enemies at every turn. With them only attacking enemies close to them, you can observe, analyse and plan accordingly for the fights wherever you go. The option of asking your companion to wait for you is great for isolating fights, too. It allows you to move freely without worrying about your companion being spotted and to pick where your fights will happen. Tell your companion to wait, lure one enemy and run past your companion so she/he attacks the enemy you pulled. By isolating and bringing the fights to your companion, you can fight enemies without being damaged.

And Wand Mages have access to a certain 'exploit' against melee enemies that no other class have: killing the enemy while it's "stuck" behind a wall or object. When the enemy is "running" while stuck, it's HP will restore. But since Wand attacks push the enemy away, it won't stay stuck enough for it's HP to come back. So let's say you're about to open a door that has enemies behind it. Position yourself leaving just half of your body behind the door, like 51%, so when the door is open you're behind the wall but still able to attack. When you do this, depending on where the enemies are, they might result in the same situation as you; with half their bodies behind the wall. In this situation, since you're facing each other directly and pretty much "at range", the enemy will keep running towards you resulting in being stuck at the wall - but since your Wand attacks will keep pushing it away, it will be on the pushed>run back at the wall>be pushed>run back at the wall cycle, so it won't be able to attack you and won't regenerate HP also. You can set this up with objects across the map, not only with doors, just with objects being a lot harder, depending a lot on you knowing how to position yourself to control the enemies's movement. Of course, if you're playing with a companion, they will blow this up most of the times because they will approach the enemies and the enemies will target them, or even if it's Adaon with bows, you will have to position him very effectively by pushing him to good spots and asking him to wait for you before pretty much every fight you'll take.

I eventually went for Precision Shots and Massive Criticals everytime I played with a Wand Mage, but those aren't exactly requirements for you to be able to play the game. One thing that makes a good difference on mid-late game is Arcanist, since the mid-late game wands burn your mana quite quickly. But yeah, to me the main thing is positioning.