If you or your organization don’t have access to ArcGIS Online (AGOL), but you still want to get your hands dirty with it, you have the possibility to sign up for an ArcGIS Developer account (here: https://developers.arcgis.com/en/sign-up/). You get access to all kinds of SDKs, you get 50 credits per month, but the best is: you get your very own ArcGIS Online organizational account. There is only one member of your organization (yes: you), but otherwise you’re able to use almost every feature of ArcGIS (for development purposes).
As you might guess: my AGOL is located at ahgvn.maps.arcgis.com.