I'm 5'10" tall and weight only 56kg. I'm trying to be massive and doing some workout daily, like push ups for at least 30 minutes, with two breaks. In the last 6 months I gained only 5kg.
I'm quite busy and can't go to gym regularly. How can I build a good physique and gain weight without going to a gym?
Unfortunately, if you really want to pack on the mass, you are going to have to pack on the weights. It sounds like in your case, you will see quite a jump in mass the first few months if you do a basic military routine or other body weight workouts.
Best advice is to just eat. Eat, eat, eat eat eat. Lot's of protein, lots of complex carbs before your workout, and then simple carbs immediately after your workout to fill those muscles. Stay low on unhealthy fats and empty calories like added sugars, beer, white flour pastries/deserts, and get on some nuts, raw vegetables, eggs, steak, chicken oatmeal, and sweet potatoes (or white potatoes in your case since you want to bulk)
Do any of the traditional bodyweight workouts: pushups, dips, pullups, situps, body-weight squats, burpees, but then after a few weeks, switch it up and do different variations of those. Do australian pullups, incline pushups, twisting situps, bench dips, ect. If you have a park nearby where you live, some of them have parallel bars and pullup bars you can use. There are people that have gotten big of just body weight workouts, but understand there will be a point of diminishing returns and you will need to stack on additional weight to force your body into growth.
Edit: And I skipped over this part because I was assuming it was a given, but yeah, post workout protein is essential. A whey protein shake is your best bet, but if you don't have that, you are going to want some tenderized beef/steak. The creatine in the red meat will help those muscles recover as well by getting more water into the muscle.
One additional key, you will want your body to be anabolic for as long as possible, and that includes while you sleep, so some cottage cheese or greek yogurt before bedtime is key as well.
As you see, putting on mass involves a lot more than just having the right workout or gym, but not to say it isn't important. All that extra protein you put into your body isn't going to do you any good if you aren't tearing down the muscle to rebuild bigger next time around.
