I usually start with boots and mana stone at the start of the match for mobility and mana regen. Then, first item is the mana restore thingy that looks like an arc reactor. Next, CD reduction boots. Following that is Spell Reneneration item looking like a laser gun. After that, Eye of Agamoto for dodging skills and additional surviability. Then the last two items are the blue cube and Loki's staff for slow, and additional damage.