No you don't. Outside of wedding world, where buying things drives the industry, and Reality TV making people think we are all to ugly to have our picture taken without professional H MU artists on site, people don't make sure all the women wear the same dress, put peach or maroon vests or hankies on dress black suits to match women's dresses, or choose just two colors and have table linens match clothing colors. If the space is nice to begin with, some sparkle and shine from glasses, vases, some color from linens or flowers, amd you are fine. Look in any old stately home, or Top formal hotel dining area, and the colors will be varied, and furnishings collected when new are in varied stages, antique to modern. If you end up with a space that is attractive to the eye, with no horrible clashes, no mixing of pastels and tiger stripes, that is great. The 2 color or 3 color decorating is supposed to be a guideline for beginners, but don't get locked into it. Use it only where it is helpful. There are people trying to make church pew seat covers go with bridesmaid dresses, when in fact guests sitting on them will be dressed, and cover the seats. Use your common sense and your eyes.
Often you do better with kids party dresses, as larger size girls bridal, like bridesmaids, are often too sexualized, bare and slit, not age appropriate. And you can easily do $40-65, where salons tend to be $80-320.