Curlers or a perm?

I really want nice tousled loose curls, like Gwen Stefani's, but I don't know how to get them! I recently bought a curling tong, but as my hair is quite long and thick it didn't give me any curls at all...

I want my hair to look curly everyday, so a perm would be an easy option, but I don't want it to go wrong, and I'm getting it bleached so I don't think the damage would do it any good. How effective are curlers? If I was to buy some bendy heated rollers how good are they? Would I be able to put them in and sleep on them every night? Would the curls result it nice tousled curls, not tight spiral ones? How long would it take to do every night?

Lots of questions... but I really am stuck on what to do!