So I recently have bought Nami, unfortunately not really feeling the whole bot support role so I refunded her.
Now I have 6300 IP and I have become very interested in jungling/junglers in general.
My question to you people is, who are relatively easy to learn and are strong?
I've taken interest so far in the current junglers: Lee Sin, Skarner, Maokai... and that's it.
If you could give me your opinion on who you think would be a good jungler would be greatly appreciated.
Thanks!

try kayle, she's easy to learn cheap champ worst case senario u only waste a couple matches and 450 ip.

Lee sin is godly but he is not easy to learn... you should try Olaf, he is very strong.

Now, if you want a really safe jungler, Warwick would be my choice, he has really strong ganks with his ult and enough sustain clear the camps without problems.

Amumu is the best jungler right now, IMO.

He was already strong, but the new jungle shifts the metagame towards him. He does really well with Spirit Stone, early ganks are crappier now because the new jungle kicks your ass so hard so all junglers. And his build path was much less nerfed than most junglers. He has Sunfire + Abyssal, whereas Skarner and Maokai were reliant on Aegis and Shurelya's. (Skarner also had Frozen Heart, but that's weaker too).

mmmm mumu always get banned play warwick just look that http://www.youtube.com/watch?v=6Cc1s2TYp6U&feature=plcp

Of the three you mentioned, Lee Sin is probably the most worthwhile if you can invest the time into learning him.

I have a soft-spot for Shyvana when I jungle...which isn't often...or well... I also have not Jungled since the S3 changes came in, but I feel like she can still clear the jungle with relative ease and quickness. The only problem is that she doesn't provide any CC and lacks any gap-closer that isn't turning into a dragon.

Shyvana is great is higher elos where games aren't just gank fests but at elos that most people play at spending an excessive amount of time clearing because of weak ganks means your lanes will lose. But her upside and why i like her is in team fights she provides a ridiculous amount of aoe damage from dragon form.

lee, khaziks, amumu, hecarim, nocturne (prob the best atm), j4 = these are the best imo and you can actually carry games with these, dont have to rely on your team getting fed cause you can get fed and just carry. mao, is a good jungler. very very strong ganks specially lvl 2 if u get Q and his W (slow/knockback, and gap closer root), however it is hard to carry with mao so you have to do your best to get your lanes fed.

Since you are junior member with limited IP, Id recommend looking at the CHEAP champs first.

Nunu is a great jungler for 450 IP. Master Yi might be decent.

Alistar, Amumu, Cho, Mundo, Fiddlesticks, Tryndamere maybe, Warwick are all 1350IP and good junglers.

Id do that before spending 6300 on someone. Ideally you use the Current rotation champs and practive jungling with them and find one you like.