Re: Warlock build
Anything that keeps you alive until you use your combo is perfect early game.
He is a devastating support even with few items SO LONG as he can effectively bond + ulti and get at least 2-3 seconds of upheaval down. If you are being focused down before that happens, work on positioning or get cheap survival items until that isn't the case.
Transitions are pretty obvious. scepter, mek, pipe, vlads, janngo, urn, wand, bracers, refresher, hex, shiva, ghost scepter, forcestaff. The last 4 are only luxuries or when desperate.