Squat. Why? You do them a minimum of 20 times a day wheather you realize it or not. Every time you go to the bathroom, get up and down from your office chair, pick up an item. A squat is one of the most functional exercises you could ever participate in AND if done properly can translate into a proper lunge as well, which directly translates to your gait.
2 point opposing extensions and pull ins. This exercise exposes a lot of weaknesses in a person and can immediately bring awareness to these areas. Core being number one as well as many extensors of the body. Use the pull in as a way to maintain controlled balance through movement. This is usually easier for someone to start than a static hold and has minimal risk of injury. Remember: the slower the better.
Variety of push ups. We use our upper body all day we live life in front of us. A push up is a way to engage the underused muscles of the triceps. However, it is important that you use a variety of positions and tempos as the chest is typically overworked on most individuals. Change up your tempo to engage the eccentric contraction, with limited equipment and unknown areas of weakness this is a way you can increase activation in those back muscles.