Apart from the general advice of getting at least 8 hours of interrupted sleep a night, eating a more balanced diet, reducing any alcohol consumption & stopping smoking, there's no 1 routine that fits every person.
In my opinion, the best way to approach "fitness" is to find a recreational physical activity that you love doing, and that you're really excited to get better at. Focussing on getting involved in that activity or sport, and learning how to improve your performance in it, will inevitably mean making lifestyle adjustments (diet, exercise, sleep, etc.) that also improve your overall health and fitness.
Fitness in itself is important, but forcing yourself to go to the gym (or eat right, or whatever), just the sake of it, sucks and isn't sustainable. On the other hand, if you put your energy first and foremost into participating in a physical activity for the sake of your enjoyment, "fitness" will just come along with it naturally, and in the blink of an eye.
If you want to try weightlifting, for example, then do a bit of research on how strength training fundamentally works, how to get yourself started with a safe and effective approach, and importantly, figure out how to fit it in alongside your existing daily/weekly responsibilities. Maybe even join a club, get together with friends, or find a trainer or coach (if you can afford one) if you need more guidance and motivation. If you decide it's not for you, then there are plenty of other sports you can try instead (and that might eventually require you to get stronger, and therefore return to some weightlifting down the road, but with a new perspective).