Depending on how you build your character.
Summoner with wand has better defense, summoner with staff better damage.
I would recommend to use the staff build, you have to avoid close range battle then it's fine. But that build is really effective in high level!
If you want to use a summoner/staff build, concentrate first on armor (mage armor, mage barrier) that will help you to get threw the beginning
Mage armor, staff mastery and lesser summon for beginning (also surge)
Then earth mastery, summoner, arcanist
Last, precision shots and massive critical for maxing staff damage (you can also try disintegrate)
Besides the first, don't max it, keep it balanced
Mage is difficult at lowlvl but it's the best character for high lvl. I just love that character!
Ps: don't feel ashamed to reskill, it's easier to use Elemental skills first and reskill the character when you reached higher lvl