Priority list for improvement

I haven’t played for 15 years and prior to that had never had any sort of coaching but played casually once a week. Now that my kids are getting a bit more self sufficient, I have some time to play. What would people recommend for improving my swing one step at a time and in what order? If possible I’d like to make one improvement until it’s set then move onto the next etc etc. I’m scoring around 100 for the 4 rounds I’ve played (48, 50, 51 on 9’s and 105 on an 18).