1) don't-- instead learn about making single page apps on the front end using React and Redux, or perhaps Angular 2. Then write a REST backend in either Node, Go, Python, or C#. Or go serverless and write the backend in Firebase.
2) if you really do want to do Django, start by doing the default tutorial that focuses on building something in the admin interface. Coming from a rails background you are on somewhat similar ground.
For example, in my industry (I work on the public sector) SPAs are never needed. Good old traditional request/response web apps, maybe with a little jquery on top to make things more responsive or add some advanced controls (autocompletes, keywords etc) are perfect for the job.
An experienced django developer can create a full traditional multi-user CRUD web app in a couple of hours. You'll just create the models and a couple of CBVs and everything else will be auto-created (but not magically created) through django-forms, django-filters and django-tables2. Now, how much time would you need to duplicate this functionality with an SPA? As I said, if you have money to burn then this is the way to go - on other cases, just use Django.
Actually it's very easy to put together a single page application today! Really easy, really fast, really practical. I'll lay out the basic steps below. But before that, an important note: several years ago, what you said was totally true. In, say, 2013, it would have been a big piles-of-cash-burning exercise to make a single page application. Today, though, it's actually quite simple, fast, and productive to create and deploy a single page application. Here are the basic steps, assuming you're using Angular 2 for example.
1) Generate your application. This is a single command line command. 2) Edit it a little, add a text box and some buttons. 3) Deploy it to google app engine; this is a single command line command, too.
The time investment is in learning how to write apps with Angular 2 or React. That is indeed a big learning curve, but it's way easier today than it was years ago. Angular 2 is way easier to write apps in than Angular 1 was. Deployment is easier than it once was.
My real thesis here is that today is a good day to embrace the modern web and try things a new way-- single page apps are actually much more straightforward and practical than they were years ago.
I totally agree that if your goal is to build a crud app for a client then Django is likely a superior approach. But if you're already a Rails developer that wants to learn something new, then SPA is a better investment of time than Django.
That will create a toy application. If you want to create a production application you need to handle data. To handle data you will need:
* Tables / lists to display the data
* Views to edit and display the data
* Forms to edit the data
* Auditing of the user actions
* User authentication + authorization
All these are not trivial to create in an SPA especially since you'll always need both server and client side code. With django (or rails, or spring or various other server only frameworks) you won't need to write client code and most of these components will be auto-generated (at leas their default values).
For your last comment, I also agree that if you know rails then you don't really need to learn django since they are both similar (however I do profer django because of its no magic philisophy and because python is a better language than ruby) but I believe that you also don't need to go the SPA route until somebody specifically asks for an SPA and has good reasons asking for it (or you want to learn the technology and modern frameworks that surround SPAs).
As a final comment, I have to say that really like all those modern frameworks (especiall react and redux) but I won't consider them for my day-to-day job since instead of creating something in 1 week I'd need 1 month using these technologies.
My favorite example is the bloatware that is Asana. I would be 10x happier if it was a using simple components written in JS but not the whole app hiding inside of a bloated SPA.
If the goal is to learn Django, then the basic tutorial is a great place to start, especially for a Rails engineer. If the goal is to build something from scratch in 2017, Django is probably not good choice for someone that's already a Rails expert.
Django would be a great way to set up an admin interface and rapidly get a CRUD interface going for an app of 20+ inter-related tables going. But the OP is already a Rails engineer, and in the modern world they're not going to be gaining much. Django is indeed a nice way to make REST backends, but so is Rails.
If the idea is to learn something new for an existing Rails engineer, then single page apps are a good choice or some other way to make backends (such as Flask) would be a superior investment of time.