1. prepared and primed to do something
now that everything is in place, we're ready to go
When everything is prepared and in place, then you can say that you are 'all set/ready'. This can relate to a task or project, or something you have been planning to do for some time. If you have a journey planned, and all your bags are packed, you can say, "I'm all set to go". You can use any variation on this expression, using 'to go' or not. "I'm all set" or "I'm all ready", means the same as "I'm all set/ready to go".