Tbh I think you should do with your IP as you see fit. If you want champs then buy them. I'd recommend saving up a little IP for a rune page. It's possible to have a great rune page for AD classes and buy a lot of champs at the same time. For me, the fun comes in as I learn more champions and play different positions all the time.
Jungle fiddle, and fiddle in general, is pretty weak when compared to other junglers in terms of survivability and jungling time.
Very good beginner jungling champs are GP, Skarner and Udyr (among others). Considering that I am Dutch I always try to get the best bang for the buck, so I really recommend champs that can be played in multiple roles. Udyr, GP and Tryndamere all work excellent as both jungle and solo top.
Build guides can be found on Solomid.net. I usually just google 'Tryndamere solomid' and take the first result as it has the most hits and usually is the best (look for guides by pro's too: TheRainMan= solotop / Reginald = solo mid / Chaox = AD carry / Xspecial = support/mid / TheOddOne = Jungle. They are the five pro players from that particular website. Their guides aren't better than those of other pro's, I just enjoy the layout of solomid)
A great way to get better is to watch
streams. You're also in luck because IEM Hannover is starting soon and there should be some great matches to watch there.