Ok. I know that your gonna be all Kuriiii <.< we were helping first. BBuuuuttttt. One of my closest friends made a rather good demyx cosplay.
This is a "tutorial" on how she made her Sitar:
spiffygremlin.deviantart.com/#/d494bljWhich I personally think is like the most basass thing ever XD its a plushie sitar
There is 2 ways I'd go about with the coat. Coats are hard, and so is vynle. SSSsssoooooo If you have experiance with Seing, try to make it, if you don't. I have another place for you to look for Coats:
www.cosplay.com/marketplace/index.php <- Cosplay.com market place.
My Friend Lanie just got an Orgy coat from someone who was selling one there. She had to do a lot of resizeing, but it was rather cheap.
As for money goes. You need the cheapest but high quality? not rreeaallyy gonna happen. I'd say that the coat will be the absolute most expensive. Its just an expensive item. if you buy it expect at the lowest $100, and you'd have to modify it.
Wigs. This is where it really varies. I see 2 styled wigs on ebay, cheapest being about $40.
If you wanted to style it yourself the cost could drop to somewhere around $20. plus the cost of hair glue if you don't have it. But I beg you, as a cosplay, get a nice wig. Bad quality wigs can KILL your entire cosplay.
Sitar: I honestly have no idea, but from the supplies ma friend listed I'd say no cheaper the $60
under stuff. look around really. Theres a thrift store here where black pants shirt shoes would be under $10, but I dunno what you have around there, it could be a lot more then that.
So at the VERY LOWEST I'd estimate... about $ 200-$300. Now don't quote me and be all like she said D8< Cosplay is expensive. thats just my estimate of the cheapest you
can get if you willing to do a HELL OF A LOT of work.
just so you now im not just bein a bitch, cause u dun know me XD
Dis:
www.cosplay.com/costume/371321/ ( My wedding Yuna cosplay) Cost me roughly $300 total.
($120 for Birtal satin, $50 for feathers, $20 for shoes $30 for tiara, $5 for sockish things, $10 fake flowers( dollar store yay)$10 for necklace, $10 Fashion tape, plus other supplies we had like chicken wire and hot glue )) and even i skipped out on some aspects ( like wig and pattern)
My best advise to you is do research. lots and lots of research. look at other demyx cosplayers and ask questions. It's really the best way to figure out the best. most accurate, and cheapest way to do things.
and as i say to everyone XD MAKE FRIENDS WITH COSPLAY.COM XD