Long sleeves are a must and weather would dictate wool vs. cotton. The shirt could be coordinated with other colors in the outfit, particularly the saddle blanket. Ties or scarves are optional and it is appropriate to show with or without them . New slacks or jeans always present a much nicer picture than old faded ones. Chaps are not mandatory but clean well fitted chaps are traditional and add to the look of a serious competitor.
Any western boot is acceptable.
Your boots should always be cleaned and polished. Any western bridle is acceptable. It should be clean and in good repair. Silver is not necessary but adds a nice touch when cleaned and polished. Optinal loose curb strap must be leather.