What courses to take before coding a fairly simple control panel?

So I've learned some php and JS here on Treehouse a while ago and it helped me to develop and maintain several websites for our small business. I'm not making money by web development, it's just a hobby for me, also saving us a few bucks.

The sites we're running are niche e-shops powered by Wordpress Woocommerce with lots of custom code on top, there are currenty 5 of them. Now I've decided to design a separately hosted web control panel, which is supposed to have some features:

1. Pulling varoius live data from our shops, like customer orders with means of fast and flexible editing it and changes being distributed back to the shop.
2. Interface for our sales personnel to add orders and customers that come from phone calls as well as other data.
3. Composing various charts for analysis from collected data combined with user-input data like our ad costs, etc. ... and maybe more!

Now while I do realize there are various professional solutions on the martket for things like that, they are either not flexible enough or too overkill. Also, I like coding!

I could go with with what I have, some basic PHP, MySQL and jQuery but I have a suspision that learning some more advanced solutions is going to pay off when things start getting complicated. So what are the instruments you would recommend?