One pretty nice thing about Ren'Py is that it isn't actually an engine, it is just a VN-focused framework built on top of an engine with a lot more capabilities - PyGame. So if you ever find yourself bumping up against Ren'Py's limitations, you could always drop down into PyGame to code more advanced features and game mechanics yourself. Another bonus to that is that (as the names imply) PyGame is a Python library and Python is one of the easier to pick up programming languages out there and it has a lot of practical uses beyond just making games. There are tons of high quality learning material all over the web, I'll link a few in case you are interested.
You must be registered to see the links
This guy wrote a few books that are aimed at newcomers to Python with a focus on game design, among a few other interesting offerings. You'd probably want to start with the
Invent Your Own Computer Games with Python book
, as it was his first Python book and starts with the most simple topics for both Python and basic game design. In fact the games he'll have you make as you follow along are all text based in that one. He followed it up with another game related book,
Making Games with Python & Pygame, this time focusing on games with graphics, and as luck would have it the engine he chose to focus on in it is PyGame, so quite relevant here. As a bonus, he has all of his books available to read for free through that site, though you could also buy a paperback or ebook version if you'd like to show your support.
You must be registered to see the links
This one's a real classic if you want to get more serious about programming. It won't be for everyone, but I've always really loved this book. It doesn't really focus on gaming or anything, but covers a wide range of important topics that are crucial to the understanding of any proper programmer worth their salt. You can also get a digital copy of this one for free as well if you'd like. There is also an interactive web version that looks interesting, though I've never tried it myself, and it's worth noting that it focuses on an older version of the book and Python 2 exclusively from what I've heard in the past:
You must be registered to see the links
You must be registered to see the links
A lot of people swear by this site and its approach. I've gone through a big chunk of the content many years back and can attest to its quality and value. It starts you off at square one and tosses you right into the deep end working with Python through the command line instead of some fancy GUI editor. It holds your hand as you get those hands dirty doing things the old school way and learning how and why things work the way they do, which is invaluable knowledge to have that many miss out on.
There are plenty of other resources out there, I could probably name several more books if I took a few minutes to go check out my ebook library, but mainly Google, YouTube, and StackExchange along with the Ren'Py and PyGame communities will be your best friends on this journey if you choose to embark on it. Ren'Py in particular has a Discord server and its lead dev (RenPyTom) can usually be found on there and is generally pretty helpful if/when no one else can answer a question for you.