If Annie is my favorite champ, and my only complete rune page is spell pen/AP...
What other champ should I pick, to utilize same runes and give me the hard-carry playstyle like Annie does?
Annie is a typical burst damage mage, if u want to utilize the same runes for other champions i would suggest other burst damage mages. here is some examples:
Anivia, Brand, Malzahar, Veigar.
@Coppersky if i understand you correctly, you want to practice the game before you move on to PVP, where you find the game play too stressing. My 1st tip would be to get a champion that does not require a lot of "skill" to play. Try to go for AD champions, as they rely mostly on basic attacks, to practice, i would suggest to get one of these ranged AD carries, (e.g. Ashe, Tristana, Caitlyn etc) and go middle vs one bot in a custom game. Once you get the hang of it, try other champions, that said, the only way to really adapt to the PVP aspect of the game, which is the most developed and deep part of the game, i'll just advice you to play Normal games, maybe start on the 3v3 map for smaller fights.
To adress snorky on how he says not to play vs bots: I agree playing with bots untill you get to level 10 is to take it a little to far, but to practice the core mechanics of laning vs a bot in custom game is something different, and as i said, playing PVP is the only real way to adapt to the game. just keep practice mate =)