You can have as many artifacts as you like. So no reason you couldn't fill every slot with an artifact, apart from the fact that you'd go nuts trying to obtain and level them all. Some artifacts fit into templates better than others, some have some nice unique abilities that are worth getting, many aren't worth the effort. You'll probably want to look at getting a few key artifacts, combining them with some dragon gear, maybe your CL5 class weapon and then filling in the gaps with jewelry items and crafted gear. I wouldn't get too obsessed with artifacts though, the game has moved on / away from TOA. That's not to say a few arent worth having, but there's often better to be had more easily from other sources.