I've tried searching a bit, but couldn't find anything. Which makes me suspicious that there is a problem with the idea. But I noticed that if I fast travel, the mana bar goes to 100%. So can I just spam spells to 0% mana, fast travel to get 100%, begin spamming spells again, fast travel etc.

Maybe it's because everyone uses custom spells instead? I haven't reached the university yet, so I haven't tried those yet.

Edit: Just using the 'wait' function might be even easier I guess

It′s because time passes as it would have if traveling normally. And as you know magicka regenerates with time, so

Yes, doing either works, but the 'wait' function is way way easier.

I did that with my Dunmer, he got to 100 Conjuration very quickly

Alright cool thanks. Was expecting there to be some kind of draw back to it.

Apart from losing immersion, nope. If you want to get both Conjuration and Mysticism up, summon a skeleton and then immediately dispel yourself, thats what I did.

the only drawback is that if they are major skills that you are boosting, and you are boosting to level up quickly, you will most likely level extremely inefficiently and make your self very weak compared to your inconveniently leveled enemies.

It's actually relatively simple to do, with your major skills.

I take Restoration, Conjuration and Illusion. Level those, and use the other magic skills to get +5 attribute bonuses.

Wait.... is it possible to DISPEL summons? Other peoples summons???????

And it only works with certain types of spells. You can fire all the fireballs you want, but if there's no target your Destruction won't go up. (Likewise you can't raise archery by firing at a target, or block by lifting your shield up and down all day as you run across country.)

Restoration works, so does Conjuration. I'd have to look to see what other types of spells can't be leveled up by just practicing.

Every school except for Destruction has some sort of really cheap Novice level spell that can be spam cast for practice. If you have access to an altar, you can make even cheaper ones if you want, and make something like a Drain Fatigue 3 pts on Self for Destruction practice.

Yes.
http://www.uesp.net/wiki/Oblivion:Dispel

Easiest Way to level magicks, besides Destruction and Restoration, is getting a Welkynd Stone; http://www.uesp.net/wiki/Oblivion:Duplication_Glitch#Duplicate_Items_Using_Scrolls it untill I'm like 2k pounds over-encumbered and Hotkey the stone, and spam the spell untill I have 100.

Either with Frostcrag spire dlc or access to the Arcane University I usually make training spells for all magic schools, they get 1-3 seconds each, for destruction I use a 3 seconds weakness on self-spell my self,works for me.
For levels it is obviously a good idea not to raise it to quickly,those training spells make it easier somewhat to handle the level so I don′t get underpowered,in particular if I′m about to raise my level and want some more points for intelligence,willpower or personality (illusion) it is easy to push it a bit with proper spell casting for choosed attribute.

Ironic that I haven′t done that lately and are way up in level with my current char and far from maximizing anything besides alchemy and destruction,so my very weak char struggle with close combat,ranged she blast enemies away rather easy,but the fighting skills is at very modest levels,all in all it is more fun now actually