Hunter and Dressage Show Clothes?

I would like to show both Hunter Jumper, Hunter flat cles and dressage this summer. My question is how do I work out buying only one outfit that I can show in both disciplines? I'm not loaded so we are going to try on jackets at a tack shop and then see if we can find the right size on ebay, but my trainer says that I need a different jacket and breeches for dressage. Can I get by with only one outfit at small local shows and maybe Youth Charity horse show in springfield, it's a three day long show. Thanks in advance.