I've never really played as a mage before.. I'm doing a battlemage conjurer now, and it's great. But I want more magicka. I see videos of peoples mages that have hundreds of magicka points. I have about 220 now and I'm level 10. Should I just enchant things with +intelligence or what?

Off topic... How can I change my username on this site? I see on profile there is a name history.

I've never gotten as far as level 10 on a Mage in Oblivion, so I'll leave that question for someone who knows what they're talking about. As for your name question, you can't change your user name. You can make a new account with a new user name, however. I've been tempted to do it a few times myself.

WALL O' TEXT INCOMING!

Hello. What is your race and birthsign?
220 Magicka at level 10 sounds pretty sizeable.
I have a mage at level 19 who has nearly 500, but that pool has been fortified with two Fortify Magicka Enchantments on his street clothes.
There used to be a glitch to get ungodly magicka, but that has been fixed in a patch. I suspect that most of the Youtube videos showing monster magicka used that particular glitch.
However, at my current level of magicka, I can make custom spells that shock and amaze my friends, and shock and burn my foes. I could even add another 100 points, legit, but that would leave me with no defense at all, and we can't have that.
As for Fortify Intelligence:

If you fortify Intelligence, it only gives you a 2x modifier to your magicka.
+5 Intelligence = + 10 Magicka
If you fortify magicka, you get what you put in. EXCEPT:
If you do the main quest, you receive the best rewards in Oblivion Gates at level 17 or higher. The Sigil Stone at the top of the tower is random.
(I save before taking the stone, so I can get what I want. I justify this because these days I only do one gate, then never again, for RP and other reasons)
Yet, many other characters have certainly done the MQ and received more stones.
What my mages are looking for is the Fortify Magicka +50 stone. Beats anything else. The best Intelligence stone you can find is +12 Intelligence, for +24 Magicka. He then enchants these stones onto his street clothes.

And then I tangent into another supporting topic:
You achieve 100% spell effectiveness if you do not wear any armor. This is only vital for mind control spells at level 25 or higher. Otherwise wear armor if you please, just know that sometimes your spells will fail, usually at the most inopportune time.
There are 5 clothing slots available to you. Hood, shirt, pants, shoes and ......... your wrist irons from the tutorial. They do not count as armor. DO NOT DISCARD. I enchant clothes with a mixture of elemental shield, and fortify magicka. If you go overboard, you can achieve maximum armor rating in the entire game, in just street clothes, making the game dull and boring. So be careful.

Tough it out a bit. Wait until level 17. If you are NOT doing the MQ, you can do the one gate, and walk away and Gates will never appear to destroy my beautiful land. The best you will find is Fortify Magicka +25 on random loot.

It's early. I'm still on my first cup of coffee, so forgive the tangent hell.

Getting more magicka has been ably discussed above.

As a battlemage conjurer however, your use of magic should not be all that high. Once you summon a helper, your magic begins regenerating and I assume you have a nice enchanted weapon to help you fight. The cost of spells goes down (dramatically) as your skill (in the magic schools involved) goes up. A master of conjuration can not only summon bigger/badder helpers, but for longer with less magicka than one with less conjuration skill. Also, high willpower helps regenerate the magicka you have much faster.

My Mystic Archer's magical specialty is illusion. She has about 300 magicka, which is more than she needs. She can cast big illusion spells (like commanding foes while going invisible). By the time the spell has done its job, all the magicka required to cast it has regenerated. She can repeat that all day long before finally popping the lone wounded survivor with an arrow. I suspect that only one who rapidly fires fire/frost/shock may need a huge pool of magicka; but then I would imagine a destructionist would want to control magicka use by getting very good with weakness and spell stacking.

My highest Magicka character among my currently active characters (Silvonwe) has a Magicka of 408. This includes one piece of enchanted gear, and will rise slightly higher when her Intelligence maxes (she's currently at 94 Int.) This is a High Elf with the Apprentice birthsign, not a combination for the timid. She could go a lot higher with more enchantment, but it's not necessary for the character, who is an Alchemist/Conjurer; she can easily cast any summon spell and back it up with Illusion, and her magicka pool builds back up quickly, before spells wear off. (And she can always restore it quickly with Alchemy.)

If you want more Magicka and you are on the PC, I highly recommend adding LAME (Less Annoying Magic Experience). It'll make magic a much more viable option - and enemy mages / atronachs / etc. in the game will become much more dangerous opponents.

Well I have Francescos mod, so enemies are quite tough right now. Mages heal if they can, near their death. He is a Dunmer with the Apprentice. He's also an alchemist, so he can create magicka potions to regenerate, as well. I'm using destruction quite a bit as well, but I'm mostly trying to conjure.

Very true. Lothran is a master regarding weakness spell usage. He also knows how to utilize Fortify Intelligence, like that was even needed to begin with

Altmer Apprentice here. Aggressive spellcaster, yet easily a one shot for any enemy magic user. Just got to level 19 and just now it takes two shots to kill me, instead of one.
I use a lot of custom spells. Some are weakness prep spells, others do a mixture as a prequel to the killer shot. I also have custom summons spells, as well as custom spells for protecting my summons, depending on what it is. Fortify Endurance for Dremora Lord for example, as opposed to Fortify Speed for Clannfear, in addition to other shields and boosts.

Destruction, Illusion and Conjuration. I require a large pool of magicka. I'm willing to give up some protection to gain that magicka.
Currently wearing:
Green Robe Hood with +50 Magicka
My old Conjurer's Robe from the University, I got it at level 8, and yet I'm still wearing it, +4 Willpower and some other things, can't remember.
My wrist irons from the tutorial with +50 Magicka

I require large magicka to protect myself from elemental spells, and do so with custom spells that do all elements at once. I also use a lot of AOE spells. It's fun to experiment with AOE paralyze and mind control as well. You need serious magicka for graduate studies at the Arcane University. It's a prerequisite. It says so on the course description catalog.

I tend to prefer aggressive spellcasters and melee characters and sneaky archers and well... sneaky thieves.

There's a couple of good ways to get more Magicka.

Use Alchemy and pump out a bunch of Restore Fatigue Potions. Only increase alchemy 10 points every level otherwise the additional points will be wasted. By doing that you'll raise Intelligence 5 points which equals 10 Points of Magicka.

Sigil Stones at level 17 and higher will have Magicka +50 points

If your a Light Armor User, The Birthright Of Astalion is an excellent choice, that will appear when your Merchantile reaches 50 and you'll need around 15000 gold to buy it. Increases Magicka by 50 and Speed by 5.

If someone dosent do enchants, but maxes his intelligence out and is a dunmer, what would the end result be seeing how his spells are mystic and illusion.

A Dunmer with 100 intelligence who lacks either items or birthsign to further boost his magicka would have 200 magicka.

Thankyou, would that be enough for master spells in illusiom and myst if the skill points are at 100?

I would think it would be enough for those "schools" of magic. The only magic discipline that really requires massive Magicka is Destruction.

Obviously, you will be limited as to how rapidly you can cast, unless you use alchemy or other means to restore your magicka quickly. Building up Willpower will help with faster magicka regeneration.

Edit: Looking over the wiki's spell list, I think the answer I gave above is correct except for possibly "Legendary Soul Trap," but I'm not sure why you'd need a Soul Trap with an AOE of 20ft anyway.

If you do some alchemy, you can craft restore magicka potions that can keep you topped off during battle. Some last as long as 4 - 5 minutes.