I relied heavily on self-made potions of http://www.uesp.net/wiki/Skyrim:Fortify_Pickpocket. Not quite guaranteed success, but makes pickpocketing more bearable in the early levels.

It seems a bit strange to become a pickpocket expert when you don't steal,

Just do it again and again. Use trainers and it will level up pretty fast. For me it is one of the easiest skills to level up.

If you're going to pickpocket an enemy, go one step further and reverse pickpocket a poison into their inventory after taking their loot. I believe you get pickpocket experience for that too, but even if not, they'll drink the poison and you can initiate combat with them handicapped or possibly dead.

If you're RPing a character who doesn't steal, then reverse pickpocket the loot back into their inventory. The NPC suffers no net loss. You just borrowed something for a minute.