another way to make gil - find a finished item to craft off of gatherable mats (ideally one that sells for a good chunk & uses few base materials), gather & vendor if need be.
just an example - I vendored probably 100 bas-relief cobalt saws leveling BSM, 10k gil total.

whether things like this are a sufficient supplement to leves/fates, or whether leves/fates are a sufficient standalone on their own, stands to be seen.