WalMart has cute clothes at reasonable prices these days...in fact I just got Norman the cutest little sailor shirt there.
I shop Target around the different holidays because they usually have cute little shirts for $1.
I hit the sales on some of the YT vendors' sites, as well as purchase gently used clothing from YT members themselves.
Petco has good sales on clothing, but you have to hit at just the right time in order to get the smaller sizes.