Not sure if there's an Ardene's in the States, but that's a good store for a bit of decora. Mostly the little knick-knacks you'd normally put on a keychain, but some are kawaii enough to work for decora. Claire's, like you said, is also a good store (I don't find it too targeted at younger girls. But..what do I know? I'm a young girl myself.)
A rule in general for Harajuku fashion, but mostly follows decora is "You don't just slap on colorful things -- alot of thinking is actually required." And, also, layers is another general rule. I've seen lot of people with colorful socks. Which I love. I also see alot of hoodies, even some in dark green or black. If you'd like, refer to this picture for a few ideas.
For now, no conventions for 2012 are in mind. I'm waiting to see if I'm able to go to Japan this summer instead. Still making my cosplays, though. Maybe next year or late this year I'll start con planning~
Miku Hatsune - FINISHED.
Matryoshka!Miku - FINISHED.
Jade Harley - Stalled.
Yuzuki Yukari - Planning.
Renko (Touhou) - Started.