Stupid Question, but how do you upgrade common craft, and what level do you need to be to do so?
I was told the fishermen can do it, but all that is avaliable in terms of common craft is "Expand Common Craft", which I believe just allows you to know more recipes.
If you mean to upgrade the skill level it comes automatically with the levels of your character. Not sure the levels but like fish oil at 20, greater fish oil at 28 etc. There is a nice fishing guide posted in the Guides section of this forum that will tell you more :)