So I just hit level 7 (booya!) and about to dabble into tradeskills. I know in Warcraft if you picked the wrong one you were fucked. So here I have a quest to pick a primary and secondary harvesting skill.
Also I'm a Novice Artificer from some quest I did earlier, does that mean I can't do other tradeskills?
What are the different types, what ones lend themselves well to a Dread Knight / tanking type?

First, you can change tradeskills, though you will lose any levels you got in your previous tradeskills ( harvesting or crafting ). That said, it really isn't a good idea to change tradeskills, as crafting especially takes a lot of time investment.

To really answer your question, I need to point out there are harvesting tradeskills ( mining. quarrying, skinning, lumberjacking, and something else, need more coffee ) and crafting tradeskills ( artificing, outfitter, blacksmith ). The latter 3 each subdivide after level 10 ( crafting level 10, not adventuring ). For now, let's concentrate on this part of your post:
So here I have a quest to pick a primary and secondary harvesting skill.

You said you had become an Artificer already. Artificer subdivides into minerology and carpenter. They make things like enchanted jewelry, furniture for houses, and are the final contructor for boats (all tradeskills make something for boats, the carpenter assembles the final product). So, with that in mind, if you wanted to keep the Artificer crafting tradeskill, I would suggest Quarrying and Lumberjacking as your harvesting tradeskills.

Changing your harvesting skills is as easy as going back to the harvesting trainer if you decide you don't like something. Not sure exactly how to change your crafting tradeskill, but I have seen it mentioned that it can be done.

Oh, and if you wanted to make your own armor or weapons ( not both ), you should try to change to blacksmith. It subdivides to armorsmith and weaponsmith at level 10.

Be warned, crafting is not simple in Vanguard, though there isn't any farming involved either, at least not EQ style farming.

I think I picked Artificer accidentally :) Blacksmith sounds intriguing.