Before your game even starts you need to be ready to set up health packs. Take Caretaker's Shrine should be used to help your Jungler if he is starting near you.
Put 2 down and 1 in your lane. 2 Caretaker's Shrine will equal more then 1 Health Pot. Then recall asap and come back to lane with full mana and put down 1 more Caretaker's Shrine and leash your Jungler. Then collect the 2 chimes near you to restore mana from using Caretaker's Shrine. Traveler's Call should always spawn 2 chimes near you at around 1:30. Already you have set your jungle up for a healthy clear and your lane with Sustain. Make sure your jungler has used the 2 Caretaker's Shrine before you put down a 2nd for your laner because you can only have 3 down at once.

Pros


+ Great roamer.
+ Easy to gank for/with because of his CC.
+ Excellent roamer because of meeps.
+ Heals can be left for your laner to use while you aren't there.
Cons


+ Ultimate does no damage.
+ Ultimate can lose you the game if you use it incorrectly.
+ High mana costs.
+ Difficult to roam with if behind.

Flash
Just gonna get this one out of the way, yes Flash is a good spell choice. It can be used offensively, defensively and for anything in between.

Exhaust
The typical support spell, this ability offers significant dueling power as well as letting you effectively "shut down" any carries damage potential in teamfights.

Ignite
The classic spell for duels, having it on supports isn't unheard of, though it feels somewhat suboptimal on Bard. That being said it does make up for his lack of early game damage, so it could be good with an adc that has strong early pressure.

Heal
Has a move speed buff on use, also the heal scales better than Barrier. Is good for sustain, escapes and chasing, but has less kill potential than Exhaust or Ignite. Only worth taking if the adc hasn't picked it up for some reason, and even then Exhaust is probably better.