I'm also making my own engine (C++ with lua integration) and here are some resources I found helpful:
- Game Engine Architecture By Jason Gregory Probably my most used resource, especially chapter 6.
- This Blog by Ming Lou "Allen" Chou (All parts)
- Lua Integration (All parts)
As a side note, I would recommend using C++ because with game engines performance is a key problem and C++ gives you so much more control. Plus using C++ will make sure you really understand everything that is going into making a game engine.