First of all, don't waste a single level-up on magicka. Why? because you can enchant gear to have at least 2 schools completely free. There is no point whatsoever in putting points into magicka, as well as no point whatsoever in using cast-reduction perks.
If you plan on ever playing on master or legendary, you NEED to invest every level up with health. NO MATTER WHAT KIND OF CHARACTER U PICK!
Don't waste your time with mage armor either. It makes a million times more sense to just go for light or heavy armor, as they will eventually reach that 567 armor cap that mage armor will never achieve. Not to mention you don't have to cast anything either, it's just there permanently.
Destruction is an obvious must, but don't waste perks. Don't use anything that isn't fire. It's the cheapest magicka cost (before you get 100% cast reduction), it does the most damage especially with aspect of terror perk from illusion granting an extra 10 damage to all fire spells. Destruction is incredibly weak at higher levels anyway. There is virtually nothing that is immune to fire except atronachs, and there is only a few things that are resistant to fire. Not to mention fire has the best AOE spell in the game, fireball ( it's also virtually impossible to miss, I might add).
Illusion is your best friend, period. Sneak+ frenzy on a group is really awesome to just sit there at watch the enemies kill each other meanwhile your just picking up loot in the other room! Pacify is also really sweet if your in a tight spot, it's your "get out of jail free card". Every perk is useful (except the cost reduction ones)
Train in Alteration up to the point where you can have 3x magic resistant perks, or spam spells to level it up. Paralyze is overrated since illusion pretty much takes care of crowd control anyway.
Conjuration is a must as well. The atronachs are great against dragons or anything with magic, since you cast the one that is immune to the damage in question. Dremora Lords are overall the best because they dish out more damage than any other summon.
Some people swear by raised undead, but I find it impractical. First of all, you need a corpse, second of all, most aren't very impressive anyway, and there is no perk to raise the damage unlike the atronachs. With atronachs you simply cast them at will and there may be situations where there arent any corpses around.
Restoration is less useful past level 10. Alchemy is your friend, and is 10x more efficient and effective at healing yourself, especially since there is no magicka cost burden. I only train in restoration up to the point where I can get the perk that makes all spells better against undead
And don't forget, before you get 100% cost reduction from enchantments, pick a high elf, equip as much fortify magicka or reduce destruction or whatever as much as you can (equipment you find, quest rewards etc). I know it's hard in the beginning to resist the temptation to put points into magicka as you level up, but trust me, in the long run you will thank yourself when your playing on legendary and a Draugr Deathlord hits you once for over 200 damage. I put every level up into health, have the 567 armor cap, as well as 85% magic resistance (capped), and I STILL am defeated on legendary if I'm careless.
REMEMBER: the single most important thing you can do for ANY character build, is max out Alchemy, Enchanting, and Smithing. They are simply a must have, and they also compliment each other. Just don't use the fortify restoration potion glitch. I'm talking about doing trillions of damage with any weapon or having trillions of health. It will ruin any and all enjoyment.