Only way that seems sustainable is to immerse yourself in the venue you are playing and scene you are in. Social Media feels like better promotion, but thinking about logistically, people reading about your gig on SM are usually at home, not out hearing music. Obviously there are exceptions to this statement, but think about your target audience. If you have a gig coming up at a local venue in a month, go to that venue once a week, get to know the other bands, let them know, rely on word of mouth.
When I released my album 3+ years ago, it hit me like a ton of bricks. I had all these friends who have Spotify, etc... and they would share my album release on facebook, instagram, etc..., but...my streams would be flat. They were not sitting and listening to my album (in fairness, it is a jazz album, so a niche genre for some of my friends). It was extremely easy for people to support by just sharing something or saying something like "cool! I am going to check it out!", without actually doing so. Promoting gigs is similar. Very easy to "like" "share" "comment" while you are sitting on the can doom-scrolling with zero intention of actually going to your gig or listening to your music.
What is the point of this? I have no idea, but I do think the façade of "social media promotion" is just that- fake. I would estimate that 95%, maybe more, of the people who "support" your gigs you promote on social media will not attend your performance. Again, MASSIVE exceptions to this rule, but for the average local performer, I feel this is how it is.