It's a credit to team Rubick guide, which avoids the difficult to farm Bloodstone. Using mana management items then positioning items, you'll be able to harass and gank then be useful in teamfights, allowing teammates to put the most effectively their abilities, depending on which spell you stealed.
After Arcane Boots and Void Stone are bought, you'll have to buy every item your team needs (Scrolls, Wards...).
Keep in mind you'll be vulnerable and a perfect target troughout the game and especially at teamfight beginnings. So never be alone.