Setting up a home gym, whether a spot on the floor for a mat and a couple of weights, or a dedicated room with a selection of equipment, is like setting up a business: it is generally better to have a plan in place than to approach it piecemeal. One wastes a lot less time, money, and energy. This doesn't mean one should buy or do everything at once. It is a way of spending wisely based on needs and resources.
What a person typically looks for from a personal trainer when they seek one out is typically different from what they look for from a yoga teacher. Just so the usual image of that a trainer looks and acts like tends to be different. Less so today, when there is so much overlap, with trainers starting to teach yoga, and yoga teachers offering individualized services that are more westernized than they used to be.
To figure out what, when, and how to eat in relationship to one's yoga practice, and more broadly to one's exercise one first has to decide what one wants as an outcome. In this, as in pretty much everything I talk about, context matters. I would say there are three main areas of concern one may have: athletic gain (broadly speaking.... this can mean gains in strength, speed, muscle mass, agility...
Most people who have enough resources to eat out from time to time have gone to a restaurant where the complexity and display of the food is more pronounced than its ability to nourish (or sometimes its flavor). This is a cultural dichotomy: simple comfort food, and food as art. My favorite meal is a cup of assam, an orange, some almonds, and a piece of bread. But I also enjoy paella and cassoulet. I just know I've been served food where breading and gravy and garnish is hiding a base that is dry and tasteless.
The exact number of asanas recognized in yoga is not universally recognized. This is partly because there are lots of variations on certain basic postures, and a there is always the question of where you draw the line of recognizing small shifts as individual postures. Those small shifts can make enormous differences in how moving through and holding the posture effects the body, but it is possible to draw the line so fine that it becomes impossible to speak about the postures efficiently.
If you were hunting or gathering in the forest a couple of thousand years ago you would need to adopt a practice of taking great care of the plants that were poisenous, and the animals that considered you as a potential meal. While a bear or a lion is unlikely to jump on you from behind the bakery counter there are plenty of traps and poisens. The same self protective way of being is helpful when you food shop today.
Every once in a while in yoga class I will find myself saying “And there we are back to Aristotle.” When I say that it doesn't mean that I want to reference Aristotle's entire philosophical work, or even his entire ethics, but that I think yoga plays out his contention that the good is to be found in a balanced state between lack and excess. To give a really oversimplified example: self starvation is bad, and gluttony is bad, but healthy eating is good.
One of the common themes of yoga is balance (physical, mental, spiritual). One of the common themes of my teaching when I am thinking about our connection downward to the earth, and the way we lift upward with control is the strong triangle. Shavasana is one of the major postures chosen for rest because it requires little muscular tension to maintain. Cat position may be hard if one's knees are compromised, but try lifting one limb and you can feel how you begin to tighten to hold the position. Lift two and this is more difficult.