I started back running at 54 after a long layoff and would recommend the run/walk method with the goal of sustained running for 30 mins, 5-7 days a week. This is good for basic fitness. (If you want to progress further, read what I wrote
below)
Then as others have said, focus on 2-3 key days where you are running 45 mins to 1 hr. that will morph into your speed work and LR day.
Then the LR day, increase by 1 mile/ 10 mins every two weeks to where your long run is at least 1:30- 2Hrs.
I followed this type of plan and am 60 yo now, running 40-50 MPW and lifting weights 3 times a week too, and am running pretty well injury free ( with a few short injuries over the last 6 years).
Also, the lighter you can get (body fat wise), will help your running and help negate impact forces on the joints.
I have found that a LR every week, and a V02 max workout of 8-12 X400 @ 2mile - 5K pace with 1 min jog rest keeps me fit and is enough to avoid injury and race 5K-10K pretty well, and even do ok at a half Marathon.
I have also done some short hill workouts like 8-10 X 30 seconds @ 5k effort, or just a hilly 1 hr. run, or long intervals like 1200s @ 10k- Half Marathon pace with 1-2 min jog rest,-as a third key workout, but have to watch it as to not go into the injury zone.
Sometimes I'll just alt. these type workouts with the 400s every other week, without a third workout in the mix. This is less risky on the old body and gives me a variety of paces to work at.
I'm not as fast as the other runners on the boards, but enjoy competing still and usually can place in my age group. Just listen to your body and back off or take off if you need to. Staying away from the edge is the best way to still run well and remain injury free, IMO. Good luck! :)