For early just go standard mid ember, even if you're safelane.
Phase Boots
Drums (cheap stats that even helps with chasing down heroes)
Bottle
Battlefury
Should be your first 4 items basically. [PMS helps with survivability]
Double Battlefury is CORE on ember, unless you are building single target. In which you get a desolator/1 or 2 daedalus'.
After your second fury just start building a crit, then you can go ahead and build a daedalus for more dps, then go ahead and get your third fury > second daedalus.
If you ever go late enough to get a rapier, save or sell one of your furies.
Basically at a standard 70 min+ game where you really need lots of damage, or need a comeback:
Travels
2 Furies
2 Daedalus
Rapier