On a 2006 4Runner SR5 4WD v6 I just purchased, what is the max tire size I can put on a stock suspension....

should I drop a couple hundred on a level kit? to get a bigger set that will fit on the front?

265/70/17 (or 265/75/16 if you've got 16" wheels) or a 255/75/17. With a level kit, you're looking at the same tires sizes, it really wouldn't allow you to go much bigger unless you did a full lift kit.

Leveling kits are cheap though, you can get one for under $50. The install may be costly if you aren't able to do it yourself. I'd recommend the leveling kit, it makes the 4runner look way better than stock. At this point though, the level kit would only be for looks (and a little added clearance).

Read this thread, it should answer most of your questions about different types of lifts, available options for each type, and also how much lift it takes to fit a certain size tire (generally speaking, each tire is different).
4th Gen Suspension Options/FAQ

What is the overall purpose of your 4runner? Do you just want a bigger tire for looks, is this your daily driver, will you be offroading/weekend camping and exploring???

If you just want the 4runner to look a little better with a larger tire and stock suspension then the 265 or 255 would look great and not hurt your MPG's to badly. If you're on pavement 99% of the time I'd just be looking at a good all season tires as this would reward you with better fuel economy.

I like the Michelin LTX

Michelin LTX M/S

Best of luck!

I would say 31.5" tires is the max before any rubbing occurs. I currently have a 31.9" tire and it rubs the fender liners on turns.

Daily driver/off-road/camping rig....i want an all around capable rig...

Ide say im on pavement 60% of the time...mind you even paved roads here in hawaii are pretty rough.

probably gonna get a leveling kit temporarily untill I can afford suspension upgrade/lift....gonna go with daystar 2.5, will I have to get alignment done after I install them?

After any type of lift, you'll want to get an alignment. Even with the 2.5/1.5 Daystar kit, it'll be hard to fit anything bigger than a 265/70/17 or 255/75/17 without trimming. A very good size would be 275/70/17, but tire choices in this size are very limited (trimming would be minor if anything at all)

The next step up is a 285/70/17. For this, I'd suggest a 3/2 lift such as the Cornfed or Toytec. You'll also need wheel spacers to clear the UCA. With this, you'll need a good bit of work to fit them. Details on what is required to fit these with a 3/2 lift is listed in the suspension thread I linked to earlier.