Being a martial artist makes you skilled. I have no idea what your definition of skilled is but it's wrong. Goku in the very beginning of OG Dragonball was taught by Grandpa Gohan, who iirc was taught by Master Roshi, who's the best martial artist in the world (which already puts him above Tao). He eventually is taught by said martial artists and with only a few days (I think), he was already far ahead of his colleagues (Krillin and Yamcha). He managed to raid and defeat a whole army BY HIMSELF, and challenged Tao twice and eventually won. He also fought to fight in 3 different World Tournaments, where fighters from ALL OVER THE WORLD fight in, and he managed to get really freaking far in all 3 of them and won the last one. He also fought Piccolo which you already admitted to being skilled so I won't go there. He was even taught by NUMEROUS of teachers including Kami, Korin, Popo etc etc.