Out main hero is very inspiring in how he trains (if you haven't seen it I suggest you take up on it). He uses mainly his Bodyweight and the Enviornment around him. Even in Gravity Training he just powers out his body whether it's 20X Gravity or more than 100X. People give a bad rap about using only your bodyweight but most of those people don't know a damn clue since their dependent on their celery sticks, treadmill running, machine loving lives to make them feel better about themselves. The real training is using your natural surroundings by sprinting, swimming, lifting logs or rocks, push-ups, squats, crawling, jumping and more. You get more in connection with the earth if you train in a more natural setting. If you want to amp up your training using basic bodyweight movements such as pushing, pulling, squatting and ab work; use various resistance stuff like weight vests and ankle/wrist weights to make the load heavier and pushing your body to the next level.
Speaking of resistance type training using only bodyweight; we may not be able to use a Gravity Room to pull us down and make us push harder but we can do certain things like the vests and the weights on our wrists and ankles but there's also levels of speed you can experiment on. Slow down the tempo of certain exercises like push-ups for example, instead of doing the same speed, take it down a notch and go a little slower to really work the stabilizer muscles and utilize your whole body to move, make a count going down and up, slow down so much it takes you a minute up and down; that is brutal. Animal Movements are another outlook to move your body for example instead of the typical bear crawl; move your body in this manner but flex the body as you move not so much isometrically but enough to where you're moving at a slower pace and your whole body feels like it's being pulled down like in the Gravity Room. Be creative and train with intention.
One thing you'll notice about how hard you train is how hungry and sleepy as hell you get after a hard and adventurous session. For me I've trained so hard at times not only do I nap a little after a good solid workout but I need to eat like a beast on a mission. I sometimes bought two big sub sandwiches or had a bowel of cereal with meats, eggs and chicken depending on what i have and top it off with 2 glasses of raw milk. I even get Panda Express and have nearly 2 of the three entree dinners just to satisfy my hunger. Unlike Goku who eats everything in sight when he's hungry, I know when my body has had enough. When you eat plenty of awesome food and sleep well, you will build muscle period. Train like your life depended on it, sort of like how Goku and Krillin from the first Dragon Ball series trained by swimming against sharks, climbed steep mountains, ran carrying milk, busted their ass on manual labor and working their hands on farm fields. You don't need to be that extreme everyday but if you want the best out of making yourself stronger and better looking, train your ass off and eat when you're hungry and sleep when you need to even if its a 30 min. nap during the day to recharge but sleep between a good 6-9 hours depending on how much recovery you need. Live on simple things and not feel like you need some crazy diet that drives people nuts and forces themselves to do.