Just my take, based on what I've read and a bit on personal experience, but also that on personal experience I can hardly be called any expert in the matter, as I'm not exactly the happiest of individuals. Perhaps part can be due to my early childhood, as those neglected at least in the first three years of their childhood have great difficulty making human connections according to a few studies, and for the fist year, I was severely neglected, and when social services found me, I was severely malnourished, following that was about four years in foster homes when the policy was that the foster parents were not supposed to get close to the foster children, the reasoning being that if the child had to move to a different foster home, it would be more traumatic if the child had to leave a foster parent they had gotten close to.
I was adopted into a great family though, and my adoptive mother was one of the most understanding and caring people I've ever met. My foster father was a good guy too, fairly distant and at the time often just tired out after work.
So that's just a bit where I come from. I guess to add, is that I was often depressed in my early twenties, and read a lot of self help books, but then moved onto studies on psychology and neuroscience when the a few self help books seemed to contradict each other on differing points, with the Mind and Life Institute's studies on meditations and Buddhism really sending me in a different direction.
Following that, I read books on evolutionary psychology, and the probably future on humanity based on historical trends and evolutionary psychology. All in all, it seemed to recognize that humanity has both good and bad traits based on what served our ancestors best, and that in this day and age, while some of those mechanisms continue to be beneficial, others are set on overdrive or are plainly unbeneficial to ourselves or others.
As to money, well the basic necessities are necessary to happiness, so as Martin Seligman wrote in his book, 'if you have enough money to buy this book, then more money isn't likely to make you much happier'.
On the other end, we are social animals, and as such, we are highly affected by how others view us (status), so people in various countries, whether or not the countries were rich or poor, the rich people (relative to the countries they live in, meaning that a rich guy in a third world country would hardly have what a rich person in a first country had) were all about equally happy. They all had high status in comparison to their more immediate neighbors, and it would likely be their more immediate neighbors that provided them with feedback regarding their status.
Then we all have our setpoints of happiness, inborn, genetic but dependat on which genes one got from one's parents (I've seen two very young kids from the same mother and father, one so shy even at three that she ran whenever she saw me, and then their one year old who would walk up to me, smile, and touch my hand without hesitation if I put out my hand), slightly raised or lowered by the environments we grow up in. So a person with very high abilities to manage and direct their emotions would even in terrible circumstances be able to find people to support them, be able to cope with misfortunes in a proactive way, while a few rich people having everything, yet they might be looking for the nearest highrise window to jump out of.
In short, I think the best we can do is take care of our basic necessities, food, water, shelter, and those things that make us socially acceptable to those around us given it's all moral (I'd probably be one of the first to defend another if I saw something as unfair despite my not being exactly high on the social scale, just cause I've been the target of meanness despite having no way to remedy whatever the person felt I deserved meanness for, and I've watched people just stand on the sides as it took place).
I'm tough, slightly discontent, and I give toughness to experience alone, I don't know how many times recently I've wondered why I go on with life (not actually considered suicide seriously though), and believe me, I've been through some of the most humiliating experiences imaginable, a couple in due to preventable stuff, like simply not drinking too much, but most in due to medical conditions to which there is little data on, and a little less to my lack of confidence in myself and especially my social ability.
Right, a few people have said I'm too honest, but especially online, where else to start but complete honesty if one wishes for honest feedback, after all, those online have little to lose if they are directly honest with me, and even mean, but I generally start discount mean people's posts (JREF is different though, I'm not as likely to meet meanness here, perhaps a bit of judgementalism, but not meanness).