What are the best skills to learn as a Sith Assassin? Like force lightning, shock, e.t.c. I like to specialize i tanking and dpsing. Also, any suggestions for the skill tree?

Hello, I would like to know the best skill tree to fall under to be powerful in pve and pvp situations. I would like to be competive and powerful against other players, but also against environment or story missions. Any suggestions?