Lots of guidelines out there. 
Getting off the couch and moving about is much better than doing nothing for sure. But as a society, we eat lot and we don’t exercise enough.
In terms of strength-based training, we should hit all the major muscle groups at least 1x week. The major muscle groups, IMO, are: chest, arms and shoulders, legs and butt, abdominals and back.
There are zillions of exercises out there, but I’m record here saying that the squat should be one exercise we always do each week. The squat covers core, back, legs, etc. The chest can be a bench, floor press, push-up activities. Overhead press, lat pulldowns, pullups, curls, etc. for arms and shoulders. Abs could be v-ups, hollow rocks, situps, etc. Just a few quick highlights.
What’s funny to me, being a gym goer all my life, and it’s a BIG generalization, is that most people fall into two basic categories: cardio only or strength only, for the most part. Sure, a few people do a little of the other group, but not enough IMO.
Ultimately, whatever you think you can do consistently each week is best for you.