well, i think it depends a lot on the context(? is it the correct word). if you want to encourage someone you can say "allez! courage!" for example, if you're familiar with the person and you want to say something like "come on! you can do it!" you can say "vas-y! tu peux y arriver/tu peux le faire!" if you want to encourage me during a race for example, you can say "allez Julien!" if you want to support a team, like in "go go go Blues!" on dit "allez les bleus!" (quite innappropriate in the current world cup...) hope this help...

come on = 1. s'avancer 2. continuer de venir 3. aller vite but Common is ....... vas-y ........... Bon courage is right in english is good luck