To be honest you dont need a trade skill. You just gotta decide what you wanna do. On siege you wont be a god with just one char, without a lot of soul stones. So decide if you wanna PvM, then make a good PvM char, if you wanna PvP, make a PvP char. If you want both your gonna have to sacrifice some PvM to make it PvPable.
If you want both worlds, make a mage, they can do spawns just fine. Sure you cant really solo a spawn, or without a lot of work, like you could with a wither necro, but it will be able to PvP.
Dont add a trade skill IMO, just use some of the resources available here. This isnt like prodo, we are far more of a community, the community as a whole is like a helpful guild on a prodo shard. If you need something made, even someoene you dont get along with, or are enemies with (factions, war, what have you), will make something for you, at a fair rate.