I think for the first ride, I would just figure out what he knows. Try his walk, trot, canter, and halt. You need these to be solid before you move on. The halt or stop is the most important
thing that he needs to know. "Whoa" should be the strongest word in his vocabulary, if it isn't already.
From the point of having 3 gaits and a stop, I would start working on steering and circles. Circle an equal number of times in each direction, to keep him balanced physically. You can set up cones or other markers to make patterns to ride through to practice.
Remember, almost anything you could ever teach a horse can be started on the ground and transferred into ridden work. If you can get him going forward, backwards, left, and right on the ground, fantastic.
Don't ride him for too long or too hard, you don't want rides to be a chore for him, you want him to enjoy and look forward to being with you and working together. Always end on a good note, if you have to leave something that he hasn't totally gotten, stop that when he takes even a little step in the right direction, and cool down doing something that he knows really well and you can praise him for as you get off.
You are definitely on the right track. In my experience, the people who ruin their first training project are the ones who don't look for and judiciously apply extra input and advice, whether from an in-person coach, a book, or an online forum.
My own book recommendation for you: Clinton Anderson's Respect and Control for English and Western Riders (I think that's enough of the massive title for you to find it, I don't have my copy in front of me, lol.) Lots of excellent exercises, whether you have a green baby or are setting ground rules for a new horse. I usually ask Scout for a few of the groundwork exercises before I mount up, just to make sure that he's focused and ready to work.