You mean, if heroes are in range of SoF, I should cast chains as soon as I cast SoF ?
It's hard to cast SoF + chains on a single target. But like Niilesh said, get in range for SoF (which you'll memorize with practice) and cast chains IMMEDIATELY after SoF since SoF has 0 cast time. But make sure you're in SoF cast range or you'll just end up casting chains first.
If you're ganking early game (for example a lane with one or two heroes), you should have full mana to properly execute a gank. Don't use your SoF + chains combo first. Use shield (which should me maxed by now) and remnant directly on top of your target. Hopefully your teammates are following you by this time. Now dmg them with your right clicks + shield dmg. Hopefully they should be running to their tower. And that's exactly what you want. Once there are no creeps near them use your chains and try to catch up with them using your remnants. Lastly you can use SoF to finish off your target(s). Since ember is so mana hungry I always build drums after phase. It really helps his piss poor stats, chasing power and retarded mana pool (don't build aquila)
I also like to keep defensive remnants if I know I can get counter ganked. Later in the game, ALWAYS keep defensive remnants while farming lanes or teamfighting. Only initiate with remnant during ganks or chasing fleeing heroes. During fights I usually hold the backline (spam SoF + chains) and rarely show face to enemies (unless I'm snowballing). Even if I get initiated on, I use my defensive remnant. Ember is very squishy and it's very easy to kill him, even if you're snowballing since he rarely has any stat items in his build except drums (which you sell late game).
Btw, silence COMPLETELY fvcks him up. Beware of heroes with single target silence (clinkz, sky, silencer). And don't rush battlefury, get it after phase and drums (even if you're the only carry in the game). Unlike AM, battlefury on ember is not a farming item (although it speeds up his farm for a second battlefury). It helps your teamfight (and counter push) and actually is a good comeback item.
I like to pick ember against tinker, NP or breed. This guy is a rat exterminator.
Edit: I think this more than what you asked for
