I'm looking to create a character with a similar skill set as Gandalf. I'm focusing in destruction (either fire or frost), alteration, alchemy, enchanting, a few points in 1H so I can effectively fight with a sword at times and possibly conjuration to give me some meatwalls to summon.

Anyone have any advice for this?

I would add illusion and speechcraft, the persuade and intimidate perks. He could be pretty persuasive, and instil fear, with people and animals.

That seems like a fairly good build, except for the point in 1H. Don't add them until you have mastered Destruction and Alteration a bit.

Also, i would consider Illusion

What are the benefits of illusion? I've always overlooked it seeing as other magic schools seem to provide more obvious benefits?

Just look at the http://www.uesp.net/wiki/Skyrim:Illusion#Spells. Remember the spells such as fury and calm are level dependent, so you have to invest perks to keep the school viable at higher levels. Perfect for avoiding combat, which can be a lot more fun than it sounds.

If you want to play Gandalf you'll have to use a console command to place your character in the "Old Men" race. There's no age slider in the character creation process.

I'm trying to create a character that plays similar to Gandalf. I'm playing a younger mage seeking to expand his knowledge, and eventually reach that level, I'm not starting as a 3000 year old Wizard

Sounds about right, but like most here said I'd add illusion. For destruction I'd definitely focus on fire, not only does it seem more like him it also adds greater benefit to the game. There are a lot of enemies out there with frost resistance and very few with fire.. If you're on the PC i'd also download the Glamdring mod, just because.

I'd completely ignore conjuration however, doesn't seem like Gandalf his thing.

Gandalf isn't 3000 years old...
Gandalf the Wizard is (if he stops living once he gets to Valinor) exactly 2021 years old.
All of the Istari reached middle earth 1000 years into the third age, and since the third age lasted until 3021, when the ringbearers departed from the Gray Havens.

Per say, but Gandalf was originally a Maia of Manw?, he was than known as Olorin. I don't want to start a Tolkien lore battle, I was just generalizing for the sake of description.

Gandalf is all about the fire, due to his ring. That would be the main focus. Apart from that you could put in Alteration (esp. the light spells) and Illusion by taking a bit of "creative license". I think you could add Alchemy and Enchanting too without getting too far away. Also use 1-H when possible. I think those six would be closest.

I thought about making this kind of Char when I heard about specifics about the game. It pretty much boils into a Battlemage with robes, so I forsee a couple problems with the build:

1. You will need to focus both Enchanting and Destruction Perks to really up the damage of your Staff. (Ex: Fire perks in both will increase a fire staff damage higher than a spell could go).
1.1. On that note, you will need to level your Destruction in order to get the damage up. If you're really determined to only use Staffs then you can avoid the Destro -% Spell Cost perks.
2. In robes (assuming you RP) you will need heavy alteration in order to stay alive up close.
3. Being that you will use a 1H sword in close combat, means you need HP and Stamina points, which will subtract from your Magicka points. Might not be a huge issue if you're using a Staff.