To be self-sufficient you need to level all crafts to 50, then meld class sets and go for masters. Since you need stuff for other classes to make items. To make all your own crafting gear you will need blacksmith, leatherworker, weaver, goldsmith. Getting them all to level 15 for cross-class skills, then culinary to 37 for steady hands 2 will make crafting HQ much easier.

Also you would want to level miner and botany to about 30 before you start on crafting, so you can go out and gather all your materials as needed. Fishing can be ignored for the most part(until level 50 its pretty useless), just level it with stuff bought of the market board for GC supply missions.

Always use food and use xp manuals from your GC, while doing leves in bulk.

For gathering, Doesn't really matter, which leves you pick(dont really have much a choice since what appears is random) to grind on, just make sure there are in your current level range, move to the next spot every 5 levels, once you out level them the bonus xp from them is harder to get, eventually becoming impossible.

For crafting there are 3 main types.
delivery ones which jgg1988 mentioned, while they pay the most xp per item, they are the worst to grind, since you have a lot of travel time(downtime)or cost a lot of money teleporting.
Triple turn ins - these can be done 3 times for a single leve. So highest xp per leve, but you are generally making 9 items per leve
Single turn ins