I can second everything that Maruno said here. I too learned Ruby and RGSS from messing around with Essentials, and I likewise found the Trainer Card to be a great place to start because of how short and straightforward the code is. I started with next to zero programming knowledge (I had maybe two classes on programming when I started here: principles of programming [just logic structures] and a basic C# class all done in the console), but Ruby is highly readable so learning it is a breeze (if you've got C# figured out, you'll find that Ruby is much easier).
I also suggest that you try out making some code from scratch once you have a feel for Ruby's syntax. Just start small, and add bits here and there as you feel comfortable. There's no use trying to make something amazing in one go. An easy one I found to start with is menus. Start by displaying the background image, practice drawing text, and add logic to it bit by bit (using conditional statements, global variables, or what have you). It may take some time to memorize the common classes, methods, and modules you'll be using in Essentials though. After all, there's an awful lot to work with. That's the only difficult part in my opinion. In all honesty, tutorials won't do a whole lot for you. They've never helped me much anyways.
