For your budget, I think you'd be better going with a high quality plain leather halter than getting a cheap silver one. Real silver isn't cheap, and the fake stuff looks it. You might find a good deal on a used silver halter, but it'll be tough imo to find that good of a deal on something that still looks good. I've never been to a mule show, but I've seen several people showing aqha/aphc/apha shows at the upper levels in plain halters or plain halters with silver buckles. I would think that having quality equipment would outweight blingy but cheaply made tack anywhere though.

Side note, I am not a mule person, but she is ADORABLE!