I have spent about a month learning Dojo Toolkit, and I all have learnt is just just the very basic stuff. The more I go into depth, the more I feel frustrated. It's totally indigestible to me. Just a few books, poor documentation and limited number of tutorials which just cover some cases. My work really depend on it, this is why I have to learn.
How can I penetrate it? What resources can help to reach my goal?
I had to go through a similar struggle too in the beginning.
One thing I would suggest as a starter is (if you have access to it) to look into the code base as well as how it's seen in the browser. Then try changing things one at a time to see what effect that has in the browser.
Another good way to get used to Dojo is (again, if your company already has a webapp or something built) to try to take on debugging tickets. I had to do that for quite awhile and I'm glad I went through that tedious process because it helped me understand the structure of the code as well as what it's actually supposed to be doing.
Lastly, try to work on your own Dojo project. It's one thing to have book knowledge of the technology but another to actually apply it. Try to build a simple Dojo project or even a widget and expand upon that once you think you have a better grip on it.
Understand that Dojo is not like jQuery. Because of its uniformed framework as well as its purpose for larger applications, it has a steeper learning curve and will definitely take more work to get the hang of it. But if you take the time to build your foundations now, it'll make your Dojo journey a lot smoother later on.