Baja's is cluttered beyond belief. It takes me forever to find anything. If I could organise it, it would most likely be by item type. Like hats, tops, bottoms, and so on. To say I have a lot, would be an understatement. I think of it more as a collection than a hoard, though.
Mine is: letters and MCs, EIs, cash shop items and RIG stuff, event items (vaguely chronologically), gold shop items (sorta organized based on what they are), game items, aquarium stuff, everything I haven't gotten around to sorting yet.
But my system is actually sort of terrible. The event items especially are out of control. So many events...
I don't organize my invo at all. It's a big, horrible mess, but I seem to do fine in my chaos. xd. I have a fairly good idea of what I own, and if not, the search bar is there to help me out. My time on Gaia is usually limited - I'd rather not spend it organizing yet another thing in my life. But I'm always jealous when I see pics of other people's carefully planned invo.
EIs and dolls and frequently used items
and everything else in this order:
I organize mine to match the dressup tabs (hats, tops, bottoms, shoes, accessories, other items), then I sub-organize by what I use most --& least. It varies sometimes, and I've kind of given up a bit. X3