I want all of that. I'd like to speak two human language fluently and without effort. I want to be in physical shape enough that it is a boon and a benefit to my mental capabilities as well as feeling good about the way I look (my emotional balance is key to my mental efficiency, depression is a near total shutdown, mania is peak performance). I'd like to do concentration meditation to the full extent possible. I'd like to train my awareness to be as wide as possible as often as possible, to take in all information, sort it quickly and without effort.
I want to be Bruce Lee meets Spock.
Stage one: corporeal
Walking for cardio health. Cardio health improves blood flow to the brain, increasing oxygen to the brain, increasing the amount of work the brain can handle. Jogging and running are too high impact for me. I would swim if I had regular, cheap access to a pool. Costs $0.
Yoga for stretching and relaxation. Very, very important. I watch videos on YouTube, I'll link them for anyone that is interested. Costs $0.
Weight lifting for general health, mental health. There are a number of scientific studies on the benefits of weight lifting (free weights are MUCH better than machines). I have the weights I need at home in the backyard, same ones I've been using for 15+ years. Costs $0 after initial investment.
Bodyweight exercise, like push-ups. Costs $0.
Intermittent fasting. Costs $0. I actually save money on food this way.
Low carb, high protein. Carbs make me sleepy, and pull blood flow away from the brain. I try to eat as few as needed but don't go crazy with it. Costs $0. I actually save money on food this way.
Good sleep. Naps when I can. Rest that brain! Costs $0.
I currently get my caffeine from drinking coffee. I balance it with L-Theanine from tea (green or Earl Grey). Does cost money, I spend roughly $1 a day on fresh brewed french press coffee and 1 quality tea bag.
Other supplements (sapho juice): Daily men's multivitamin, zinc, fish oil, pygeum, lectithin. Does cost money, but makes a noticeable difference. I'd estimate it at roughly $1 a day.
Stage two: mental
Meditation. There is no substitute and nothing that compares to directly training your brain. If you are here because you want to get the most out of your grey matter, meditate! Costs $0.
Language study. I speak two languages. Costs $0.
TED talks. Another anon had a good criticism about TED talks, but I still feel they are of some amount of benefit. Just because something is easy to consume doesn't mean it isn't worthwhile, that's hubris. I like deGrasse's Cosmos as well, hell, I like educational programming in general. Too much Square One as a kid, I guess. I'm open to alternatives. Costs $0.
Reading. Can cost, but there is so much good stuff to read that is free. I've found that the older I get, the less fiction feels beneficial and the more it feels like filler/entertainment (even stuff like Asimov).
Stage three: immaterial
Art. Art fundamentally changes the way your brain operates. In order to make any real progress in art you have to learn to see things differently, which means you are training your brain to see things the way artists do. There is a reason so many people I respect in history were polymaths and artists.
Yoga. Like art, yoga fundamentally changes the neural pathways in the brain. "Self-control" is a practiced skill, ask any martial artist. Yoga trains your brain to overcome the complaints of the body, clears the mind, etc. I train in all eight aspects: internal moral living, external moral living, body poses, breath control, sense control, concentration meditation, contemplative meditation, holistic meditation.
Moral living. Live frugally. Low karmic impact living. Yama, niyama, basically be good to yourself and be good to others (everything is interconnected).
Meditation. Meditation cannot be stressed enough. It is the direct way to manage my own brain. Reduces stress, make all of the above manageable. Technically a sub-section of yoga but worth mentioning again on its own.