This really depends on the length of time you’re planning for the workshop, where it will be held (in person or online), and what your goal of teaching is!
I would suggest keeping each workshop to 1-2 hours, with the opportunity for everyone to ask questions at the end. You can create a simple PowerPoint presentation with the content you’ll be teaching. You could also create handouts for folks to take home afterward (these can easily be prepared in Canva). You can rent out a space or host the workshop over Zoom.
For promotional content, you can create it all online for free on Canva and post it on your social media, website, and ask your friends and family to share it too.
For ease, here are two great articles explaining the important steps in creating a workshop: