Although not the closest from Gili islands, Bali is the island where most people are arriving from when visiting Gili Air. Many different boat companies are operating from there in 3 different harbours : Padangbai, Serangan and Amed. The tickets can be bought basically everywhere in the touristic areas of Bali but we strongly recommend to get them several days in advance. If you like, Atoll Haven will be happy to organise everything for you from the pick-up at your hotel to your arrival in Gili Air.
Bear in mind that almost every company is departing from each harbour early morning (before 10:00 AM) and that if you need a later departure, you will have to take a domestic flight from Bali to Lombok !