I've been gone a few months, just came back today so maybe this is out of date but for me the easiest way to make money can be boiled down to a few simple steps.
1. Become a subscriber which allows you to have the max amount of crafters.
2. Sell your mats, if this is your first time I suggest Biochem and it's supporting skills because you will make a fortune selling your mats on GTN and more importantly it will make you overpowered no matter what class you pick.
3. Level up, the higher your level is the more crafters you can send out.
4. Don't delete your characters, even though I've been gone for six months I have a small army of crafters and while they are working I am playing the game. After a few level 50 characters you will make millions in a few hours.
The huge catch here is that it's a grind. First you have to level up your characters then comes the fun times of loading each character to send the crafters out and you will be emailing your alts constantly. There are people out there who can make millions selling their crafts but that was hit or miss for me mostly miss. My way is boring but it's a sure thing at least it was six months ago.
I came back just for today and this method still works. It's also the reason why I'm not using the rest of my 30 day subscription it's boring. A sure fire way to make credits, even on a slow day like today when no one is playing but not fun at all. I wish I could tell you how the real crafters make serious money based on the mats they buy from me but that's one egg I could never crack.