Molten Strike. What do to next?

Hello, i accumulated around 600d and im thinking what to upgrade? I was considering to collect a little more and buy original sin, or totally diffrent, swap amulet to simplex amulet, armour to rare and sword with fire per 10 strength. It would be awesome if someone could help me choose which one would be the best.
POB: https://pobb.in/XP8N7VJzr4qE