My core build, common for most suports, usually is:
Flask/2Sight - Philo/Sightstone - Boots - Aegis+Bulwark/Boots2.
I might get Eleisa's Miracle if I have of money, but wasting 1100 gold on merely extra sustain is very iffy. Particularly because I usually will end up getting Shurelya's Reverie sometime and therefore rebuild the philosopher's stone, and because I usually take exhaust rather than heal as a support.
But yes, Bulwark rush all the way. The item that really starts to help your team out, and also helps make your support more tanky so you need not die every single teamfight - since supports are generally squishy.
Shurelya rushing is also a common build I tend to see, but I don't encourage nor do I follow it often myself. That extra ms, while providing a lot of potential utility, does not have as much a large impact on teamfights to justify its early build.