In the Evolution PV, her denim outfit was from a store called "Nude" in California. If at any time she wears a teeshirt in her PV's, it is either MTRLG (for recent PVs) or it could be from the 88 Tees store. The Rainbow PV featured two denim outfits (orange & pink) from the MTRLG line. The Free & Easy PV were also probably MTRLG line clothing. I think the dress for the Moments CDS was Anna Sui. The Inspire CDS dress was Ungaro.
For her 2005 wall calendar she wore Bulgari jewels, Christian Dior, & D2Squared.

In any case, I don't think the brands should matter because Ayumi does have a stylist who helps her with things. The fact is, she only wears the stuff because she can afford to. I don't think she's wearing such obvious branded items in her daily life (in other words, her clothes are all a costume)