OH MAN LET'S SEE
I'll just name some I tend to use whenever....[[ok so, like, i'm sorry for the large paragraph LOL]]
Off the bat, I'm just gonna throw out there that no matter the colour scheme, I love using the mini headwings/headbows to balance the use of each colour out *V*
Black/Cream/White (by cream I mean the shade of cream used in Little Lucie, idk why but I love coming back to that even though it's pretty damn hard finding matching shades outside of the little lucie items...rosamund's yearning matches though so between the two sets I can usually muster something up; although, that's why I use the white - there's not enough legitimate cream on this site that fits the category/look of the Little Lucie sleeves/skirts and the Rosamund stuff)
White/Off-White (The colours I use the most, tbh XD I find them the easiest to use, surprisingly enough; depending on the outfit, I tend to throw in touches of silver; thankfully, quite a bit of the silver items on the site are in the same shade. The April birthstone necklace is pretty cheap and adds a little sparkle to many of my outfits, and I love using the debutante crown whenever I can [it just sucks because it doesn't layer with very many items])
Gold/Red/Black (hnnggg why is the gold-ish hue of Bound Warlock kinda hard to come by? Actually it's probably closer to bronze...but I swear some 'golds' are more orange than they are gold and it sucks. Gold is such a nice colour to throw in as accents but that nice, rich gold is very, very hard to come by, I find. Silver is much more easier to incorporate, which sucks because sometimes gold is what works the best and I hate having to settle for silver hngg)
Off-White/Black (This actually can be tricky because I hate it when all the shades of an outfit don't match and there's several different shades of both these floating around...Though if you give it enough time, it's not as hard as I'm making it out to be LOL. Balancing the two in an outfit without a third colour is a bit hard for me, though, and I'm still working on it >> [as proven by the last colour scheme I mention])
Brown/Light-Brown/White/Off-White (This is mostly for the casual stuff Gaia releases, as supposed to the elegant/fancy stuff; e.g. Autumn Days and, like, the Sketchbooks [of course, just the original/a FEW of items recolours], oh! And the 'Portrait of a...' items ;u ;!! I'm kind of pulled away from the autumn look as of late, but I love going back to the cardigans and the ankle boots the site's released in the last couple of months)
Red/Off-White (I tend to use a deep red more often than a brighter red, but I lovelovelove working with red despite how little of it I own, sadly LOL. I finally got my hands on a Garnet Millennium last night, and couldn't make an outfit with it orz. Its a WIP, I guess, but I'll figure it out 8D)
Black/Silver/Off-White (This one I started using purely because of Rose Legend's colour scheme, and it quickly turned into one of my favourites [maybe bc of how easy it is to come by items that match LOL] butbutbutttt the silver is always a great finishing touch, and the off-white helps balance the outfit out bc otherwise it would just be all black with touches of silver [which isn't bad but] also bc the rose legend legmod has touches of white on it, and that has to be used again SOMEWHERE in the avi Bl)
I also tend to stay away from the awkward shades that Gaia likes putting out (some of the greens), and I don't ever use orange. ; O ; Orange or green, really, but sometime I'll make an exception for green. I also really dislike the bright gold(?) that some of the older items have (e.g. The Sandman D8 It's my most FAVE item but that gold and that red....nothx I'll stick to the hair).
Pastel colours are also a lot of fun to work with, but I find I can't make 'em look as good as others do so I tend to stay away from them LOL orz. I also love the dusty rose Gaia puts out a lot, it's quite nice to use with off-white/white 8D
redface
I think I went overboard...
EDIT: I'm such a dweeb omg I'M SORRY GUISE I WENT BACK AND ADDED SOME MORE OPINIONATED CRAP //runs