As some of you may remember i got this game 3 weeks ago.

since than i am now on my 5th character (i was trying to find something i like to learn a bit about the world in game).

I stuck with a mage. Actually the premade build.

I am now level 12 after about 50 hours (broken leg can’t do much else)

have not really done many quests as i am having far too much fun killing vampires, making people follow me on command, you know:)....i think it says i have done 18. Got to the arcane university to make spells but than stopped.

i don’t use any armor. But i gave my robes shield enchantments so i have 17 defence (don’t know if that’s good at level 12)

But my question is do you use weapons?

A normal fight is - Paralyse, summon flame guy, than shoot fireballs like mad.

but then i run out of mana i run and drink potions... should i have a weapon too?

Also where is there really good robes for shield?

this is my current set up so you know.

2x rings - 32 point feather.
Necklace - Light 14 points.
Boots - Detect Life on 14 points
Trousers and shirt - Shield 14 points.

2nd part first..
I would suggest you get through the mage guild recomdations, and enchant some items yourself, then you can enchant 20 point armour clothes.
Since you're not using a shield lose the necklace and take a torch instead, only wear the feather rings after a fight, try to restrain yourself in what you grab..
( I should really listen to my own advice here, I'm such a hypocrite ).
This will free up alot of room for other enchantment effects ( shields ), when you can make them yourself.

1st part second, a dagger is a good idea in general, unless you rp a character that never uses one.
some creatures may be immune to certain spells, or as you found you may just run out of magic..

Brew loads of self made restore magicka potions, and learn to take your time in dungeons, vanilla Oblivion I remember stages out most fights so just wander around after one fight before leaping into another.

Also whats your willpower?, as having it high helps speed up magicka restoration.

I don't bother with shield enchants for pure mages. If you're getting hit, you're doing it wrong. You lose out on 3 enchanting slots as it is, so I stick Fortify Magicka wherever I can. Maybe it's just me, but I don't like Flame Atronachs. I much prefer something that can take a bit of a beating; it can act as my meat shield while I lob spells at the enemy. If you're not already doing so, be sure to incorporate 'weakness to x' into your routine; makes things die much more quickly.

A weapon changes gameplay alot - not better or worse, just different. A mage certainly does not need a weapon. My character is a no-melee mystic archer, but when she runs out of arrows, she doesn't have much trouble. And she doesn't really use elemental destruction spells.

With her bow on her back a fight might go like this: Command spells to get everyone to kill each other off while she remains hidden. Eventually there will be only one foe. She finishes him with a combo spell (invis on self + summon clannfear) - the invisibility even allows her to safely lead her clannfear right into the face of her enemy.

These tactics don't use melee or even destruction and are very very magicka efficient. While her foes or summon are fighting, she is safely hidden regenerating magicka.

17 ac is horrible at any level But it sounds like your biggest problem is running out of magicka.

1) At lvl 13 you can get +40 magicka sigil stones from Oblivion gates. These will help a LOT.

2) You can also get a much better light enchantment from a sigil stone than you can make. Likewise with detect life, although with good light this shouldn't really be necessary. Jewellery enchanted with Night Eye is another option.

3) Carry a staff. Do the first Arcane U quest. You can choose either damage (shock is best) or a paralyze staff. Since you like to start battles with paralyze it would be a big magicka saving. Also you could buy the staff of Apocalypse from Rindir's Staffs.

4) Make a good Shield spell for when you need some protection. They're more effective than your 17 ac and are cheap to cast. You can combine it with whatever spell you use to start battle.

5) Carry some Welkynd stones for real magicka emergencies.

6) Consider doing the Thieves' Guild line. I am in love with Nocturnal's Cowl!

Mara

My mage characters usually wield a silver dagger. Primarily to apply poisons.

I don't really do pure mage's anymore but for sure have some type of enchanted dagger in your pocket in case you run out of mana, good enchantment would be probably absorb magicka or health. Probably going to need to recharge it fairly often though but that shouldn't be a problem for a pure mage haha.

I recommend doing the first proper mages guild Quest
enchant some jewellery with either fortify intelligence or willpower.(or strength) get some robes or iron armour to enchant.

Personally, I would ditch the robes in exchange for street clothes, unless it breaks an RP. You get five slots for clothing. At level 17, Oblivion Gates will spawn the best-quality sigil stones. Right before you take the stone, save your game. The sigil stones are random. If you don't get what you want, reload your save. I get Fire, Shock and Frost Shield 25% and put them on three slots of clothing. The other two slots (I saved the wrist irons from the tutorial, as they are weightless, and do not count as armor, thus keeping your spell effectiveness at 100%) go towards Fortify Magicka +50. Doing this gives you an effective Armor Class of 75, at its base, no other shields or enchantments or spells, and you never have to repair it, ever.

My mage carries a backup blade, usually a shortsword or sometimes even a claymore. And a staff. And a bow. He can clear out entire dungeons using only a bow, as this is his, and mine, and all my characters' true love. I use the bow for the intial shot, it is usually poisoned. Then use destruction magic for the rest. I break out a blade when I'm about to overwhelmed and svcked into melee combat. I don't do well at melee combat, so I try to keep them at range. This is where a claymore is very useful, as the radius of your swinging claymore, is long enough that you can hit the enemy, they can't hit you because of the length of the blade, and you fire off hardcoe touch spells in-between each whack. Practice with it, there is a sweet spot. You don't need to use a Power attack to keep your enemies at bay. Just careful jabs keep them out of reach, thus preserving your fatigue for that killing blow should you need it.

Welkynd Stones will recharge your Magicka instantly. Carry a couple of these around, they can be real life savers, you can use them mid-combat.

It's not a really efficient use of your blue bar, so it can work for one or two fights before you need a break. Try only to use paralyze touch spells and then only as an emergency if you get swarmed at close range. Paralyze is extremely expensive. Frenzy, calm, invisibility, and summons can play the same role for less money. 1 second paralyze is the strongest, because the enemy still has to get up off the ground. The actual duration of disabling is 3-4 seconds for the cost of 1.

Since you use destruction spells, stick with undead summons. Daedra are more powerful and expensive, to the point that it's pretty much all your mana can be used for. Undead can still take a lot of hits and have some nice immunities.

Conjuration has a lot of great contingencies. If you're fighting atronachs, try summoning zombies because zombies have a ton of health. Skeletons use Block so they're nice vs. melee as well as cold or paralysis foes. And anything that uses normal weapons can't touch ghosts or wraiths. Turn Undead is about the cheapest spell in the game and completely turns them off. Use it on necromancers' summons and laugh.

The main thing about daedra summons is that they work fast and hit HARD. But you pay for it of course.

A mage can carry a weapon for blocking. Blocking will cause an attacker to recoil, and you can move away and get the chance to cast something.

One of the most powerful destruction effects is drain health. Even if you make the duration 1 second, if you drain all the target's health, it dies.
As for enchanting, I second the motion to use Fortify Magicka. You can cast shield spells or whatever you want, as long as you have enough blue stuff.

I would drop the robes for common clothing. The Dark Shirt, Mages Hood and Dark Pants work perfectly since they have zero weight. Next get to LV 17 and do a couple Oblivion Gates. Save before the Sigil Stone and Get Frost 25% Fire 25% Shock 25% Detect Life 180 and a Magicka +50.

I wouldn't Paralyze every enemy I would just Paralyze opposing Mages and Tough Enemies. Don't forget that waiting 1 hours will restore your magicka

Should you use a weapon too? Well, considering that you can thereby add an additional damaging magic that doesn't count against your magicka, I'd say it has to be a pretty good idea, unless it goes against some kind of role you're playing.

Carry a silver dagger to deliver your alchemy made poisons.

The best advice I could give to any type (warrior, thief, mage) is; know your enemy.

This is my power build.

Race: Breton
Sign: Mage

Class:
Destruction
Alteration
Illusion
Mysticism
Restoration
Conjuration
[Anything for the last skill.]

For the equipment I do all fortify magicka.
And

You want your magicka as high as possible with 100 willpower. There is a formula that uses willpower and max magicka to determine your regeneration rate. Once my character is well along they regenerate faster than I can spend the magicka.

Shield is best cast manually as well as any light or detect spells as that helps you level the schools. I just recast all of these as they deplete even if I'm running around doing nothing. I also use a restoration (fortify magicka) and a conjuration spell in the same manner. I try my best to make customs of each that last 120 seconds to cut down on the spam a bit.

Keep in mind spells like shield stack, so you can cast several at once to easily cap your armor at 85.

Another trick that works well is make spells that are too expensive to cast and be effective. Make a 6-10 second restoration spell, fortify skill 30-50 of the school. Now you can cast much stronger spells.

Also don't use paralyze, damage fatigue is cheaper and it lasts. Not sure how long because I got bored waiting for the test subject to get up.

Now the weapon is actually your most important tool. Get Azura's Star.
Soul Trap 6 seconds
Weakness to Magicka 100% 6 seconds
Weakness to [your element of choice] 6 seconds. I use fire personally.
Use summoned creatures to feed the weapon with Azura's Star.