I’d suggest 3 moderate workouts, you should get a lot of volume in on the basics for now. Leg raises (and/or planks) are great, it’s a good idea to do a core exercise. I would suggest also working on back bridges. My main concern is that you don’t stress the shoulder and elbow.
Speaking of which, I think you should focus on inverted rows instead of pull ups for now. They are easier, sure, but don’t underestimate them. When done properly, they work to stabilize the rotator cuff muscles, and give a nice back and biceps workout. Plus, they will help prepare you for pull ups. I still suggest doing them once you do pull ups though.
Ensure that you feel very comfortable and strong with these basic exercises, perhaps a month or two, then consider working on pull ups. Just watch your shoulder and elbow, don’t push too hard!