Is there material (articles, lectures, etc.) you've found useful for designing games? Either for inspiration, or nuts and bolts process, or something else?
Uh probably. I've written a bunch of essays myself, and have actually gone back and re-read them and remembered something useful (I do not wish to put in the work fixing them up to be unembarrassed enough to post them). But I've also read plenty of stuff that qualifies, Richard Garfield's essays from the Duelist, Mark Rosewater's articles and blog, wait it won't all be Magic. Knizia's dice book? I don't know if I learned anything from it but I did read it. Richard has a good essay on luck that you can find on youtube. I guess he's done it multiple times, here's one:
https://www.youtube.com/watch?v=dSg408i-eKwMark Rosewater has had more to say about game design (focused on Magic of course) than you will find the time to read/listen to. Like, he has a podcast called Drive to Work; he realized that he wasn't getting good use out of his time in the car, so he records a podcast sometimes then. He was putting up one a week and built up a backlog and so switched to two a week. Anyway you can endlessly read/listen to his stuff. I don't agree with absolutely everything but he certainly has tons of good advice.
I've gotten a lot out of games themselves, both what to do and what not to do. Like, in a typical game of mine, there are cards with rules, and on a typical card with rules, there is a line at the bottom giving the card types. That is from Magic (I don't know if Magic got it from somewhere else). It doesn't always survive in published versions because you can also identify cards from the backs, if there are types but they aren't mixed and you don't have multiple types per card. So for example in Gauntlet of Fools, the prototype says "Weapon" at the bottom of Weapon cards, and the published version doesn't. But both versions label Encounters, since there were more possibilities there in the same deck.
Anyway play some games, learn what you like and what you hate, that's a good start for anyone.
Prior to reading William Poundstone's book Prisoner's Dilemma, I didn't know about dilemmas. Probably that book and Magic have inspired me the most. I made all these games that either had dilemmas, or Magic's interacting rules-on-cards, or both. Cosmic Encounter would be a big influence except I first got that stuff filtered through Magic. D&D has probably had an effect, even though in my day beyond "it's rules for swords & sorcery make-believe" it was a mess. Being a math guy and a computer programmer has had an effect.