Fiddlesticks was my first IP champ. I liked his Drain, because that meant I could stay in lane longer and not have to recall (I hated recalling when I started out, haha). I stuck with AP mids (mainly Heimerdinger, my second IP purchase) in my earlier days before settling on support as my main position of choice. Oh, I should note that I played bot Fiddlesticks in those days (I didn't feel comfortable enough to lane alone, haha), and didn't even dare to try jungle until I was forced to as Nunu when playing with a couple of friends. It didn't go so bad, but it was definitely a learning experience!
I believe Elise was the first champion I bought with RP, but she wasn't what I had expected and promptly refunded the RP to put toward Zyra (I think - it may have been Xerath).