Obviously, there is no one-size fits all for fitness; this is something that worked for me, the injury I dealt with, and getting ready for multi-day hiking.
I had six months before hiking season started again so I mapped out out a brief outline of where I wanted to be by then and worked backwards to zero, so-to-speak. It was tough to limit myself to it, but I stuck to walking 5 minutes a day for a week. Then, I added 5 minutes each week for 6 weeks. This was probably the most challenging part for me since I always left wanting to do more.
I would alternate walking and running 5 minutes at a time every other day for up to 2-3 miles. On the off days I would use my rowing machine for 10 minutes, sometimes going up to 20.
At that point (about 2.5 months in) I started alternating my workouts through the week.
Day 1: 1.5 mile run, working on my speed to get my lung capacity back, stretching & body weight exercises.
Day 2: fast walk with weighted vest (50lbs) on an inclined treadmill, stretching & body weight exercises.
Day 3: Rower and walking
Day 4: Rest
Day 5: 3-4 mile run, stretching & body weight exercises.
Day 6: Rest from the home gym, but always busy in the yard or garden
Day 7: weighted vest on inclined treadmill
I was able to stay fairly consistent with this for the remaining 3 months and by the time summer hit I was more than ready to hit the trail!
Each hike that summer was progressively harder with more distance so by the time we were faced with 17+ miles in one day it was a no brainer whether I could do it or not.