If by gym you mean weights, then yes you do Not need weights to get Buffer.
All kinds of body-weight exercises will give you tone, strength and more muscle mass if done properly with proper nutrition.
- For 6 packs, you need both abs exercises with good nutrition (to lower body fat percentage)
- Push ups are amazing for chest, triceps and even core. You need to do variations
- Pull ups will give you the V-SHAPE and more muscle on your back. Also, You need to do variations
Now i recommend that in addition you :
Squatting not only tones and builds legs muscles, but it empowers ur core, helps you build 6 pack muscles and produce much more growth hormones and thus help u add muscle mass.
Same for burpees, it is what i call "explosion" workout. Once you do it u will understand, you will get sore muscles even places where u never knew muscles existed.
However, please do these two exercises step by step, with good posture because if you don't take care you might injure urself.
(i injured my knees because i overdid burpees and i was kinda jumping diagonally not straight..
I got what is called Plica Syndrome and my doctor said i have to rest from leg exercises for 6 weeks. However if you do it properly you 'll see its probably the best bodyweight exericse for power, tone, fat burning and muscle mass increase).
As for variations i highly recommend mark Lauren's book, it has around 111 bodyweight exercises variations with full routines for different levels (beginner,intermediate,...)
