My current play though is with a mage summoner and I'm finding the build fun, interesting and rather durable.
My thoughts: Go summoner from get go. That little Sparkling is better than he seems, and will give you practice in using a summoned ally. That and the 20% increase in secret finding will help with both traps and getting access to the high level secret doors that hide the best loot.
I would refrain from investing heavily in spells, and use those skill points to max out Staff Mastery and, of course, get Lessor Summoning maxed out. Maxed out Staff Mastery coupled with a Sparkling will make short work of most enemies. I got Level 1 bolt, and Level 1 Ice. Those served well, esp bolt as it has a stun chance. At higher levels, Bolt III is useful for the Arc.
Griss is a good Companion, and I'm very found of her, but at around Level 6, you should be able to get Hirge. Hirge with a shield / heal can last a long time in a fight, and heal you through long dungeon runs. A mage really needs a Companion to keep enemies off.
I skipped getting a Fire / Ice summons. I didn't seem to need them, given the little Sparkling pulls his weight. So when I got access to Icemist I was able to invest those skill points into Earth Mastery III. The Iron Golem is a beast. By mid-game, buying a few Fire / Ice summons scrolls is pretty easy so when you need one, you can just summon it via a scroll.
The Iron Golem becomes you're go-to summon in big fights, and the Sparkling serves as a back-up summon, or for general use when clearing a dungeon. Again, that little guy is more useful than he might seem.
As for weapons, the Staff of Storms is a great go-to weapon for most the game. It does good damage (esp with Staff Mastery), uses ZERO mana, and has a stun chance. It will serve you well. Getting an element based staff to swap to as needed is helpful. Saving mana points to use for Summons will help.
At higher levels, you can consider investing in Aracanist, and it's prerequisites.
Note, investing in Arcanist and Earth Mastery, is really skill point heavy so most players might want to choose for one route or the other. So if you want to go Summons, make sure you go that route.
The skill Summoner is worth it. The skill will increase your Iron Golem by a few levels, which is a pretty big difference in fighting ability. The increase to other summons is just a huge plus.
An Iron Golem will make short work of the Arena, save for the troll fight where he proves comically ineffective. Just make sure you summon the Iron Golem in the ready room that way he's ready to go when you enter the actual arena fight.
The troll fight is a different story... oh, how those trolls just won't stay down. It's got to be frustrating from the Big Metal Guy.
Very interesting tips and helpful but I want correct somethings :
1- arcanaist lv 2 more then enough unless you want fight bosses or quick farming In sunken citadel use 4-5 arcane staves . When you have spare points and there no skill for them use it for arcanaist lv 3.
2- since you summoner no need for spells till you reach ark, that time lvl up lightning spell to 3-4.
3- maximize staff mastery and lesser summon first, put 1 point in mage armor (opinion) but recommend.
4- go fogas forest and farm werewolfs for huge amount of xp with death-fire elemental staff I recommend fire staff and farm there till lvl 13 its ez don't worry pull 1 by 1 as usual after that go do your quests I recommend icemist quests for mage first there useful items and ez xp.