[keg in kc]

You can start to gather as soon as you enter the game. Just head to the fleet and pick up the gathering skills. But as Pants said, you can't actually craft anything until you have a companion. One way to boost early xp that I do on all my toons is talk to all the crew skill trainers on the fleet. You'll be level 4 before you fire a blaster on your starter world.

I'm only crafting for myself. I've never really been able to get a feel for playing the auction house in any of these games. So I'm not the best person to answer that one...

I am getting a kick out of cybertech. The space mods really help on the missions (not that they're hard...) and I like having something other than the pre-order STAP to ride around on. It also gives armor mods and mods which are helping me keep my gear on-level. I hadn't planned it this way, but as it turns out artifice is a great partner skill for that because it provides enhancements and hilts, so the only thing I can't make myself right now is blaster barrels. Synthweave isn't all that beneficial right now, but that's as much because of a lack of recipes (on my part; there's tons in the game) as anything else.

Each of the crew skills grants a certain benefit to your character, too, if you explore them enough. Biochem, for example, can give you bind-on-pickup (BoP) artifact (purple) level medkits that are not consumed upon use, which I would imagine could come in very handy in operations later on. Cybertech gives you BoP grenades that aren't consumed as well as BoP speeders. Synthweave gives you BoP armor. Those are just the ones I've done personally. I'm sure the others give similar boosts.