Beforehand I have to say that I’m not that familiar with making a Chrome cosplay since I’m not a Chrome cosplayer myself.^^
But first of all: Which version do you want to cosplay? As with nearly every KH Reborn! char there are quite some versions of her. Maybe if you search the web or artbooks and stuff you might find one where you actually already have clothes in your cupboard
If you want to go for her main clothes you should think about your skills and the time-limit. Are you familiar with sewing (fabric’s always cheaper than costum-made costumes) or do you know someone who could help you? Since the top of her schooluniform could be a little tricky as it should fit accurately. Pleated skirts on the other hand are rather easy to sew (even without a sewing machine) or to find. But first of all I’d browse ebay and look for second-hand clothes or in cheap shops and try to alter the clothes if they don’t fit the original perfectly. Although as already said: Difficult with the top of Chrome’s schooluniform.
I’d advise to pay a lot of attention to the wig since this one is the most characteristic feature of the Reborn! chars and clothes can always be altered or other outfits can be cosplayed. I usually “ebay” my wigs. Just search for Chrome Reborn for example and you should find some already styled ones (although these might take about 40$). Or if you think you have the guts and skills to make the hairstyle yourself you could also find just a longer dark purple wig and cut and style it. Might be a little less expensive but maybe not thaat much and maybe for the beginning a little difficult.
Since your budget is rather limited in my opinion I’d neglect her purple eyes and not go for lenses. (Besides I never wear lenses myself, since I feel about them nearly as Tsuna does in the beginning xD) These can be photoshopped if you really want to be that accurate about it.
The eyepatch you could make out of a small piece of leather or fabric and the skull could be painted onto it for example. Or you do the version with the band-aid
, which is a little easier^^.
I hope this was at least a tiny bit helpfull^^''