I am not NEW to pure mage, but I am also not a veteran. However, I will give you some advice based on my travels thus far:
- It depends on what you mean by "pure mage." In the beginning I started off with light armor. The alteration school helped boost my armor rating with oakflesgh and later stoneflesh. I never spent a single perk point in light armor and my character's skill in light armor is still rather low. I think it is below 25 because I started off as a Breaton. Also, I hired a mercenary (Jenassa) early on as well, which kept some of the attention off my mage. Once the alteration skill was high enough, I took the MAGE ARMOR perk and replaced my set of light armor with robes. I have never looked back, but in the beginning my character needed that extra protection to get started.
- Additionally, I also carry one-handed melee weapons. In Skyrim, I would say maybe 75% of encounters are with melee combatants who are up in your face, and spending most of the game queuing up the Benny Hill music and running away from everything is not appealing to me in the slightest. Also, there are a lot of cool enchanted weapons in this game that I like to take advantage of. Finally, those melee kill cams are so satisfying. I am currently level 25 with exactly 60 skill in both one-handed and destruction. Even the enemy mages in the game have melee back up weapons.
- Destruction part 1: The novice level destruction spells are garbage after level 4 or so. I have been using the apprentice fire bolt spell though for the last 20 levels or so. One reason though is because the fireball spell at adapt level needs to be used with some caution. It is a strong spell, but an explosive spell and will damage "friendly" NPCs who are in combat and they will turn hostile to you. Also, in one fight (no spoilers) I charged up an d threw a fireball spell at a boss and my follower Jenassa ran in and got one-hit killed by the boss and my fireball spell connected right after and did the final lethal damage to kill her. As a follower, mercenaries are marked in the game as "essential" and cannot die, except if you deliver the final blow, which I did. As a role play, I refused to reload my save. This boss also raised her as a zombie that I had to fight off and made for a compelling personal story line moment for my role play. Another time I was fighting a dragon and a fireball connected from a distance right as a hold guard decided to jump into the battle out of no where and I started a second rebellion right then and there apparently. Just be aware of your destruction spells.
- Destruction part 2: As I have gotten to level 25 with my 60 destruction skill, I cannot cast expert level destruction spells for half magicka yet (nor can I find any books for sale yet anyway) and my adapt level spells are no longer getting the job done against these high level enemies. I play on "Adapt" level difficulty settings and while others claim that anything below "expert" is too easy, I can tell you from experience that anyone who says that treats Skyrim like a video game first and a role play second. they exploit the already stupid AI any way they can and guzzle potions at instant unrealistic speed. If that is how they have fun, great, but if forced to have actual combat and save their potions for after combat or that rare moment in a break in combat, then I would have to ask if adapt is too easy for them. But I digress... I play on adapt difficulty and there is a pendulum swing back and forth between a new spell or perk that makes my destruction spells one-hit-kills and then I level up to a point where I need new spells because my now old ones can't get the job done anymore.
- The restoration tree doesn't look too appealing to me, but it does have a branch where you can earn a 25% and later 50% permanent magicka regeneration bonus. So that is worth putting a few perk points into for sure.
- I personally have no interest in conjuration. There isn't a deep pool of creatures to summon to choose from. Just a wolf, a wolf on fire, and deadra. The school of conjuration is pretty much "the dark arts" so unless you want to be a necromancer who also summons creatures from the plane of Oblivion, stay away from this school. I do. I might mess around with it another time as a necromancer role play but not for my main mage character.
- Illusion is a school I have almost never used. I try the fury spell in a group of bad guys and that is always fun and funny to watch them turn on each other, but finding such groups to cast this on isn't that common. often enough it is only between one and three bad guys, and when it is 3, often times two of them are lackeys you can one or two hit kill, so a fury spell is a waste of time.
- Alchemy is interesting, but I already gave my opinion on potions in combat. outside of combat they can be interesting too. I just haven't messed with it yet. maybe in the future when i get bored. the same with enchanting. I like finding enchanted gear. my friend showed me with his character how enchanting pretty much breaks the game once your character is good at it. Once you are good at enchanting, you can be "good" at everything else by creating enchanted gear that fortifies your other skills. Are you a novice at picking locks? that's okay, just wear some enchanted gear and now you have 100 lock picking!
- So, if you want to be a "pure mage" I have to again ask what you really want out of it. in my time so far, i liek beign a blend of mage adn combat simply because i like using the weapons and items in find as loot, and I personally agree with my friend, that you "should" limit yourself to what enchanted/magical gear you find on your own, because enchanting your own stuff cheapens the game play experience (at least in our opinions).