Design a t-shirt

We are a gymnastics club that require a t-shirt design for our gymnasts to wear to training. The gymnasts age ranges from 2-15 and must be a unisex design. We have club colours of navy and gold and a logo. The design will be printed on a white t-shirt. We are looking for a bright and modern design. Our moto is "Believe That You Can"(B.T.Y.C). I have attached the current t-shirt but the design requires a fresh look. On the back of the t-shirt, include "BTYC Gymnast"