So i've never jungled before but i'm getting a little bored with the typical positions on my team. I wanted to know if there's a way to jungle at level 20 without falling behind and putting your team at a disadvantage, and what champions you suggest.

I know I can get Tier 3 runes at level 20 but I can't afford them. Therefore the runes I have available are all Tier 2 with 6 Marks, 6 Seals, 6 Glyphs, and 2 Quints.

I appreciate any advice you have to offer, Thanks!

You won't be able to jungle Ezreal yet, but you should be able to survive the jungle even without T3 runes. I know I could. I still have a weird rune page with AD marks, armor yellows, and AP quints and blues :O. Just make sure you have at least 21 points into defense in your masteries. I like to go a bit more for the tenacity and stuff.

For sure you could. Pick a champ wit good sustain to start with WW, skarner, mundo, elise if ur good with her, I cam clear the jungle without usin all my pofs with her.

Check Stonewall on RoG for a good overview of S3 junglers:
http://www.reignofgaming.net/tier-li...ist-thresh-era

Like Wylwist said, focus on those with good sustain. Assuming your Seals are Armor, that will help. For Masteries, I would actually put 2 points in Butcher, and possibly others in the Offense tree depending on your champion. The key Defensive masteries are the ones that increase health and reduce physical damage, plus Bladed Armor - so you don't really need 21 points there.

Now, go play around against bots to find a couple of jungle routes that work for you, recognizinig that what is ideal for a 30 with Tier 3 and a hard leash is probably not the best for a 20 with Tier 2 and no leash. (You may get a leash at 20, but don't count on it.) You need to figure out when you can realistically gank (i.e. you have buff(s) but are not too low on health) and when you should base. It can take a bit to work this out for yourself, because you can't just steal something from a guide in most cases.

But it's definitely doable.