Basic starting supplies for a bottom lane poke support. Spellthief's Edge helps you harass, push, and builds into a decent active item, Frost Queen's Claim. The Total Biscuit of Rejuvenation helps you sustain after trading damage with enemy laners. You and your marksman should both be starting with a Warding Totem so you have some ward coverage for the bottom bushes too.
Alternatively, you could start with Ancient Coin for the better regeneration. The item it builds into, Talisman of Ascension, is also pretty awesome, but Spellthief's Edge means stronger laning/poking.