Ways to advertise website with mathematic courses?

I own website with 1500+ mathematic videos for primary school/middle school/high school, targeted for my country only.
For each course i take roughly about ~9$ monthly or 22$ quarterly.

I have started doing SEO some time ago, still waiting for results couple of days.
I have facebook page with ~600 likes/follows and I am about to start Instagram F/U after some warmup.

Do you have ideas what else should I do to bring people in?

Seo is going to take a while to get visitors in. I would recommend google ads to bring in traffic to your webpage.