I really want to try this out but I'm having a hard time putting all of the pieces together. Here is all I have so far:

Appearance: Really long gray beard and hair.

Weapon: Sword with spell/staff in off hand.

Armor: Mage Robes w/ magical armor.

Am I missing something? It seems like I'm missing something.

Speech. The Istari were forbidden to match power with power, and instead were supposed to motivate mortals to oppose Sauron's forces themselves. You'll want to level up your Speech to do that effectively.

Unfortunately, Speech doesn't help much in many of the quests in Skyrim.

I'd also say pick up all three of the crafting disciplines, as Gandalf was quite knowledgeable, and that's a good way of reflecting that, even if you don't actually use them.

You should also use Wards from Restoration, and Sunlight spells if you have Dawnguard. Also Candlelight from Alteration. You really should be using magic from all the schools of course, but if you're going to use offensive magic, it should probably be fire, given that was Gandalf's specialty.

I'd put points into speech and try to intimidate people. I'd also try illusion and alteration, as destruction seems a little over the top for Gandalf.

I would mention getting Frost as your horse, It's been a while but I recall Gandalf's horse being white.

Sorry Hagrid, I'm a big Harry Potter fan, but Gandalf wins this one.

That's a actually a really cool idea.

Aren't the horses in Riften white? I was thinking about aiming for Gandalf the Grey (if there is any pure white robes I can enchant them but I don't know of any)

Riding a white horse in addition as well as white robes would be epic.

I was planning on taking advantage of all the magic skills, and speech including persuasion and intimidation.

Thanks guys keep the suggestions coming in. =)

Shouts, they're a form of "speech" and don't the wizards of that world use a form of spoken spells? If so then shouting would fit the bill.

Enchant a sword and name it Glamdring and use a staff in the left hand...there's a special silver destruction staff that you can get during the MQ if you have the slow time shout:

Remember in the first movie when Gandalf was scolding Bilbo about the ring and the room went dark? I think he said "Bilbo Baggins! I am not a conjurer of cheap tricks. I'm not trying to rob you. I'm trying to help you."

That scene really shows the power of just using his voice.

Ok everybody this is the backstory I've come up with. I'm really new at this but I've tried my best. If you know anything that I've left with "none" please share with me because I thought for a while and couldn't come up with anything.

If you had the "live another life" mod, this would be so perfect.

Still, sounds great so far