Happiness Without Material Comfort Is Playing on Hard Mode
Even though you can certainly achieve happiness and mental health without financial health, the truth is in modern society, most of us understand that financial wealth can give us freedom. It can give us time. It can give us peace. You're not gonna buy your way to happiness, but you will buy your way out of common causes of unhappiness.
In olden times, one of the routes to finding peace was you would become a monk. You would renounce things; you would renounce sex, you'd renounce money, you would renounce shelter, you would renounce attachments, and you would go off in the woods. After 30 years, if you'd finally gotten over the fact that you weren't gonna have these things, then you might find some peace. When the truth is, most of them probably never got over it.
There are lots of monks out there, but not a lot of enlightened people. I think it was Osho who said, "Every time I meet a prostitute, she wants to talk about God, and every time I meet a priest, he wants to talk about sex." Whatever it is that you deny yourself will become your new prison. If you have a desire for material comfort, it's actually gonna be easier and faster to fulfill it in modern society, if you know what you're doing and are capable.
Then, it will be for you to renounce it. It'll take a lifetime to renounce it, and maybe then it won't work. But you can make some money and be materially successful in less than a lifetime. You can get there without it and probably have a more lasting form without it. But that's playing on hard mode.
Physical health, of course, is the foundation of everything. If you don't have your physical health, you have nothing. Another great Confucius saying that I liked was that "a sick man only wants one thing, a healthy man wants 10,000 things." When you're sick, when you're down, all your other desires run away. Without the ability to get up and function, you can't turn into this desiring machine that you are.
Physical health is actually the most important, but I speak the least on the topic because I have the least specific and unique knowledge. I'm not self-actualized in that regard. I'm in okay health, okay shape, and I have an OK diet. I understand a lot of the theory of it, but I would feel fraudulent giving you that theory unless I were a paragon of excellence in that domain.
Whereas, I think in wealth, I'm much more self-actualized. On the peace side, I've gone from being a mostly unhappy person to being a very happy person, and that I think was deliberate. It was practiced; it was based; it was through realizations, and I made progress. So, I have a chance to tell you what worked for me.