It's okay if not all of your pieces match because if your main pieces go together, it won't matter. Your nails should match what you're wearing. Your jewelry should also match but your shoes and hair accessories don't have to.
Let me give you and example. Sometimes, if your pants or skirt has multiple colors on it, you can wear a plain top that matches one of the colors on it and wear a hat that has those same colors in it too. Some colors that commonly go together well are pink and purple, orange and pink, blue and yellow, blue and purple, blue and brown, turquoise and tan, green and purple, purple and turquoise, red and pink and yellow and blue.
You just can't wear anything that doesn't match on days that you have somewhere important to go but if you're just playing at home or hanging out with your friends, you don't have to worry so much about matching your outfit perfectly. If you have all of the same colors on, you are matching too much and that will make you look bad. I never like to match too much.
Have fun matching!
Junior Fashionista
Aimee Terese