Oh, I don't even know where to start! Hm. I want to give as much information as you might possibly need, because I'm guessing you can't really ask your target questions. heheh. I hope I don't forget something important!
I'm a December baby, a Sagittarius leaning a bit into being a Capricorn, and a Fire Tiger in the Chinese zodiac. I'm a "Winter," as far as colour compatability goes.
I'm 5'10", a brunette, and very, very pale (rosy-pale, not yellow-pale). I don't tan, but I do get freckles. I'm not really a small person, so I can pull off large/bold designs rather well, if you feel so inclined, but smaller/more delicate things are great too!
I prefer my bracelets to be around 7" long (my wrist is ~6 3/4". I like a slightly loose fit.). I like bracelets to be ~7 1/2" if it's something wide, like a cuff. If it's claspless, it needs to be 8" around or bigger to get it over my hand, I'd say (~9" if it isn't stretchy at all). :p I do prefer bracelets with clasps, generally.
I love all metals, but I tend to wear silver most often (this might just be because I own a lot of it, though). Copper is good in bracelets too, because I have (Junior) RA. As far as I know, I don't have any allergic reactions to anything. [Nothing so far, anyway! Copper bands do turn my skin green, but only when I seem to really need to wear it (go figure)]. I love antiqued metals, but prefer un-antiqued silver (oxidized relief/details are okay though!) Brushed metals are cool too.
As far as colours go, I love pretty much anything, except pastels. I prefer bold (jewel tone) colours, and seem to look better in them. Of course, that doesn't matter as much with accessories (yay!), so I can get away with wearing colours that don't really look good on me in large quantities. The only things I would say looks bad (horrible!) on my skin are bright oranges and most opaque yellows, so please try to avoid those as main colours! I'm not crazy about "candy pink," either. Fuschia pink is lovely, though. :D Cobalt blue is my absolute favourite colour, but please, don't feel limited to that. ^-~ I adore colour, so anything will be wonderful!
Favourite gems/stones... Much too hard to choose. I love stones. They make me happy. ^-^ (Absolute favourites? Things like labradorite, kyanite, sunstone, 'goldstone', etc. that have unexpected flashes in them. I love surprises! :D)
Materials.. anything you'd like to use! Stones, wood, crystals, seed beads, fabric, glass, plastic, shells, pearls, metals..everything! Just have fun! Oh, I do prefer plastics (lucite, etc.) to be matte, though. I love texture (both visual and tactile), but the 'shiny' plastic feels weird to me.
As far as general style goes, the only thing I don't really like are "charm bracelets." (ie. a chain bracelet with lots of little charms hanging from it. Other danglies are okay, but large quantities of charmage, not so much. :p) Other than that, go wild! ^-~ I wear a wide variety of clothing and love a wide variety of styles. I'm excited to see what you come up with!