My college had a gamers' convention this past April. I heard the word "convention" and decided I HAD to cosplay. ..I was the only one there in costume. X3 But it was fun! I got to DDR in this. XDXD
In case you live under a rock and don't recognize the character, it's Princess Peach from the Mario series. Specifically, this costume is based on her Super Smash Bros Melee design.
(you can see the character
for example, and here.)
My mom actually did all the hard work for me. XD I just picked out the fabric, and she sewed the entire body of the dress, including doing the bows on the sleeves and attaching the lace to the bottom. Crazy amazing, she is. X3
The gloves (and petticoat X3) were bought as is. The shoes (which you can't see, haha) and wig were also bought, but had to be altered. I cut the straps off the heels and tacked on little gold bows. The wig was more complcated.

I had to buy extensions, then I had to sew them into the wig, then I had to curl them, which took forever. >>; And then cut and hairspray the heck out of it. XD
The crown was made from the bottom of an aluminum vase, cut to shape, covered in masking tape, and sculpy clay for the patterns, and painted gold. The gems are glass (my dad uses them in stained glass, usually) and the pearls are a trim I just cut and glued on. It was sewed into the wig so it wouldn't fall off. X3
The big gem and earrings were impossible to find. I ended up making them out of resin. ...But I screwed up the mixture and made them all cloudy and bumpy by accident. >>;; Obviously my first time using the stuff. If I ever wear the costume again, I'd have to remake those. Also, the earrings were HEAVY. o_O I made them with two earring studs a piece, so that the weight would be supported by two of my holes. (I have three in each ear. ^_-) I was so worried they were going to rip, but, no! Yay for dangerous cosplay. X3 X3
Oh, the gold on the dress is a kind of thick fabric. I cut it to the proper shapes and glued it on with fabric glue. Yup. That's about it.