Gmail is getting full, does creating folders help that?
Assuming you're talking about your storage quota, no.
Gmail doesn't have "folders". It has "labels". They're just like tags you can add to messages to help find them later. A message can have multiple labels. (Unlike a folder, where a message can only exist in one at a time.) "Moving" a message to a label will not free up any storage in Gmail.
You might also have a look at Organizing your mail.