There are a lot of articles on gamasutra (also GDC videos on youtube) on different aspects of this, but the quality and exact applicability is going to vary a lot, here's a couple of short ones that call back to psychology 101 that may be useful. For me personally the core gameplay/learning experience would need to be interesting/useful for the the other 'gamification' features you are thinking about adding would contribute to my motivation, you might be thinking about cause and effect backwards here. I remember learning to type when I was a child because the game that taught it was so fun (standards were low back then) not because I really wanted to learn to type.

https://www.gamasutra.com/blogs/JosephKim/20140323/213728/Th...

https://gamasutra.com/blogs/SitaVriend/20170804/303075/Intri...