The suggested order of viewing the docs is the following:

Get started
	- Install and set up
	- Using the API
	- System requirements

Working with the API
	- Overview

gis module
	- gis module
	- class gis.GIS
	- class gis.Item
	- class gis.User
	- class gis.Group
	- class gis.Tools
	- class gis.ContentManager
	- class gis.UserManager
	- class gis.GroupManager

lyr module
	- lyr module
	- class lyr.Layer
	- class lyr.ImageLayer
	- class lyr.FeatureService
	- class lyr.FeatureCollection

viz module
	- viz module
	- class viz.MapView
	- class viz.WebMap
	- class viz.WebScene

tools module
	- Geocoder
	- Geocoding
	- Batch Geocoding
	- Reverse Geocoding