how are people going on about managing regulars and marketing?

Heyo, I'm a small owner and been running my place for about ~2ish years now.

I see a couple of same faces every once in a while. There's a guy who comes in almost every Thursday, always sits at the same spot. I know his name & usual order, but I have no way to reach him, and if he stopped coming in tomorrow I probably wouldn't notice for a month just because of the amount of things going on at once.

Tried making a Google Sheet at some point to track regulars and figure out what was actually bringing people in. Lasted maybe two weeks lol. There's just no time.

Also on Doordash and Uber Eats and I run stuff on Instagram occasionally but honestly have no clue if any of it does anything. I've spent maybe $100ish but have no idea what ROI i'm getting.

Just wondering how other small independent spots handle this. Are you tracking any of this stuff or just kind of going by feel? Has anyone found something that actually works without being a whole thing to maintain?