I should say that going to the gym might not be as effective as bodyweight exercises such as squats, push-ups, and pull-ups. If you look at the different variations of just push-ups (forget about pull-ups and squats), you'll see that they each concentrate on different muscle groups. Moreover, if you understand mathematics well, it should be evident that changing the angle by using a chair or a bench will dramatically increase tension on your shoulders and other muscles. So, doing bodyweight exercises is a great way to go. One problem I see with many of my friends is that they get motivated to go to the gym, but in the best circumstances, they quit after just one year. Also, in my opinion, trying to make a habit of going to the gym doesn't work well, as to get visible results, you need to put in more energy than your body is willing to give in most cases. This means you have to rely on willpower every time, and this resource is quite limited. Personally, I find bodyweight exercises more effective because, first, you're less likely to get injuries. Second, you get more satisfaction from exercises like muscle-ups or angled push-ups than benching 100kg. Third, bodyweight exercises include mainly natural movements, resulting in more balanced results. And fourth, the most important, you don't need to prepare a lot before exercising, as gyms may be far away, closed, or crowded, but your legs and hands are always with you. I have managed to study and exercise for four years now perfectly, so people who say you can't do both simultaneously are talking nonsense. I am 19 years old now, and I don't find push-ups any less effective than dumbbells or going to the gym, as exercising regularly is much more important than quick results that would eventually disappear when you stop. In the long run forming a positive link between exercising and good mental health is the most important thing from my experience.