In local shows, no. You want to look good. But you don't need to look great. As long as your tack is clean and fits. Same for your clothing.
These are two of the girls in my riding instructors show teams. Not much bling. But they look good. Her show team likes to colour coordinate (cant spell for the life of me so I hope you know what I mean if I spelt that wrong lol) and I love the way it looks when they do. But its not needed. I have seen people show in a nice shirt and clean jeans and they place as well as they deserve to place.
Look good. But have fun!
And I agree, look into what equipment may be needed for what your entering in.
**after posting I realize the picture uploaded twice! But I can't seem to get rid of the 2nd one. Sorry**