Squats, sit ups, push ups, pull ups, bridges.
Cossacks, alternating leg lifts, hs push ups (against a wall), chin ups, rolling neck bridges (wrestling neck training).
Alternate between these two groups each week. Do 50 of each each day; so 50 [squats, sit ups, push ups, pull ups, bridges] each day 1 week, then 50 of each exercise in the second group the 2nd week, and so on. To make it more intense do them faster or slower or change your form.
Each month add 25.
After 3 months change shit up, add exercises or change the reps so that you're doing more squats and sit ups or something.
GOMAD or just eat a shit ton.
It's ez.