First, congrats! You did something that others would shy away from, be proud of your accomplishment. I know a lot of educated programmers that struggle to put a system together enough to make it functional for anything other than a developers machine. You made a production system that helps your business. I am sure it is far from perfect, almost NO system is perfect regardless of who designed or built it. But if it saves you money or makes you money it is already a success.
As for learning. IME reading and experimenting is the only way to do it. Yes, structured learning will go a long way, but even than, doing is the best teacher. You'll do something and make it work than 3-4 months later look back at it and be like, OMG that is so horrible I cannot believe I did it that way. The reality is that is true for all of us when we are learning, and frankly after 20+ years I can still look at stuff I wrote say last year and be like damn, I could do better today. New grads coming out of school require a few years of experience to become proficient and honestly it isn't their education that is bad, it is just that doing is the best teacher many times. I spend a lot of time showing young devs designs and things only experience can teach you. I have also seen new grads come out and they obviously have been spending their time experimenting cause they freaking rock it from day one, so experience & experimenting is what matters.
As for selecting tools, systems etc. My advice is stick with what is proven most at this point since that will typically have the most support on places like Stack Overflow and in general forums. This will also mean you can get design ideas and assistance from books and online resources easier and faster than if you try to adopt bleeding edge tech. For databases, stay with SQL for now, postgres or mysql are both fine choices, I'd favor postgres but honestly that is personal preference. If you are in a Microsoft stack and have those tools, stick with MSSQL and Visual Studio, great tools and tons of resources. For coding, stick with common frameworks and languages, Python is totally solid. Understand too that a tool that is awesome for backend work, or computational work etc may not be the best tool for UI/Web work. For example, Python is awesome as a backend tool but I wouldn't recommend putting together Web UI's with it. You can as many teams do, but the level of effort and lack of common resources makes it harder than say using Javascript/node.js or even Ruby.
For algorithm, curve fitting, regression type stuff, don't forget to check out Khan academy, and also check out youtube there are some awesome people posting great content on there (just pay attention to recommendations here cause some youtube content is crap too).