Fishing, mining and botany all can net you some good gil. Simply selling the mats you get or using them yourself to level up your crafts is a good idea.

As said, vamps throughout the easy levels of leathworking will get your some great gil, just selling the vamps from the toadskin levels alone got me about 1mil, and soon i'll be doing the highest tier of toadskin vamps which i'im sure will get me near another mil.

Besides that, arrows sell really well. I've stockpiled a lot of vulture feathers and soon i'll be on my way to making about 100 stacks of silver arrows, for a total of 4mil after i'm done.. and i have most of the mats already!!

For BSM and ARM, you can HQ items easily at the higher levels. I've found HQ tools/weapons aren't that hard to make, and finished items are easier to HQ than components.

With alchemy you can break down fish into shards/crystals, or break clusters into massive amounts of crystals. Leveling fishing and alc at the same time is a great idea, as you'll have plenty of fish to rank up and it's smooth sailing.

For weaver, you can make the R21 underwear, or level it up as a subjob for other crafts. Not sure what else with wvr makes a lot of gil.. HQ items I'm sure.