Try first to do calisthenics's, as it's a great foundation in general for fitness. It will help with core muscles, some exercises are: Plank, Russian twists, ab crunches, leg raises. Though for arms you will most probably need to use weights as the only possible calisthenics's exercises you could do are chin ups and push ups. For legs you will 100% need to do weights as squats and lunges become quickly not enough to build muscle and strength.
Four hours is more than enough. You could go 2-4 times a week to the gym. Try doing fully body as it is quite good for beginners. Do a bit of cardio as it is just good in general and can actually improve muscle gains, do it on separate days from weightlifting/body training days, or after workout.