Mk V Furnace

Personally I'd say if you don't spend money I'd only buy pieces for 300 or the golden pieces for 750, the rest you get better value off refreshes and farming. Especially for the furnace now that you don't have to decide between mkIII droid callers and mkVI syringes.

I'd say keep the crystals and farm

EDIT: That is of course if you have the needed furnace salvage from rancor raids