The are 2 different ways across 2 unique modes of transportation to help you travel from Abadiania to Guarulhos. If you're only considering the price, you should check out the bus out of Anápolis towards São Paulo, as it is the cheapest to Guarulhos. It's common to find tickets for as low as $71. Real Expresso operates from Abadiania to Guarulhos, so you book your trip with them! Book as soon as you can, as there may be limited availability.
For these medium length trips, it's important to book your tickets as soon as possible. While there are bus or by car transportation options available, the sooner to book the better. While prices for buses or trains might not fluctuate as much as flights, their availability certainly will. It's recommended to book these flights at least 2 weeks away, but even more if you are able.