It's pretty easy for me to tone and put on muscle if I go to the gm regularly. I don't get dramatic bulk increases, and I'm finding that in order to do that I'd really have to be putting more time and concentration than I can afford at the moment. I think no matter what happens gaining weight is probably going to be very difficult for me to do, even though I definitely think it's possible and would not rule it out as something to pursue in the future.
What I'm interested in trying right now though, is a way to increase the natural energy level that I have daily. So I will probably be adopting some kind of system that takes into account 3 major things.
1. Proper breathing and breathing exercises
2. Aerobic exercise and stretching
3. Good hydration
Ultimately it comes down to properly oxygenating your body. Most people, myself included, don't do a very good job of breathing properly but it's probably the most key foundation of proper health. I've read stories of an old aikido master who practised deep deep breathing and overcame some pretty insane diseases, breathing techniques are also extremely prevalent in yoga and other similar practices, and most recently I started looking into the "Nishino Breathing Method" which is all about achieving health at a cellular level through breathing. The science behind proper oxygenation is real even if the practices seem more spiritually based.
The aerobic exercise is similar and activity-based and people are generally conscious about that sort of thing. Stretching, though, I think is in some ways very underrated. In Yoga they talk about the concept of "chakras" and in ancient chinese medicine energy "meridian lines." The idea essentially is that by combining stretching and breathing (hello yoga) you will increase the flow of energy in your body by becoming more flexible, limber, and allowing stagnant energy to flow more freely.
As far as good hydration goes, I have some doubts as to wether drinking tons of water all day is actually good for you. Anthony Robbins talks about eating "water-rich" foods as opposed to flooding your system all day. It fits the models I've always had and makes more sense to me.