I have allways been very small(i ran 2 marathons easily years ago).
In the last few years i lifted a bit and added about 8 pounds of real muscle.
At 57 soon i will buy a gym membership with the modest goals of adding a little muscle, keeping my full mobility and slowing the aging process.
I plan a daily routine of about 40 minutes.
Day A- KBell swings, pulldown, pullback, vertical pulls
Day B- squats, shoulders press, dips, push-ups
Day C- yoga
If i feel the need i would do it in 4 days, A,C,B,C Repeat.
I am on a 30 years plan.
Thanks for your comments and input.