I haven't read the entire thread, but some things I've learned over my adult working career (I'm 43 now);
1) Start early. That's cliché at this point but it's so true and often looked over. I joined the Navy when I was 23, and started contributing 600/month to their version of a 401K at 25. I've continued to increase my contribution ever since, and the magic of compounding is real. My sister, on the other hand, is 32ish, and hasn't started anything yet, all while making a lot of money as a travel nurse. Every year she waits, the less prepared she'll be at retirement.
2) I'm never going to be good enough or have the time to spend to become good enough to time the market, therefore I subscribe to the John Bogle method of investing. My 401K is a simple 3 fund portfolio designed to minimize fees, expenses, and taxes. I carry the premium class of Fidelity's total market index, total international market index, and total bond market index, and I use their Brokeragelink so all my trades are free and now those funds are essentially free. I recommend reading Bogle's book about investing to at least learn how much money you lose in fees and expense. Maybe you're lucky enough to be one of the rare people that can time the market, but I'm not one of them, and this method of investing is simple and as long as the market continues to deliver its historic performance, my nest egg is going to be tremendous. It also maximizes diversification.
3) Take advantage of the "mega backdoor roth IRA" as soon as you can. As my income has advanced, I've been fortunate enough to be able to contribute the full 55K/year to my 401K. Anything after 18500 (2018) is after tax contributions. I then roll those after tax contributions to a roth IRA so that now that money is growing tax free. I'm "incomed out" of contributing to a roth via the traditional means, so this "mega backdoor roth" is a fantastic vehicle which is also now recognized by the IRS. It was called "backdoor" because it was taking advantage of tax loopholes, but now the IRS fully supports it.
4) Pay yourself first. This is why I'm just now going to buy my first BMW. I decided that I wanted to ensure I was preparing for the future before partaking in luxuries. I have no need for an M2, but I have a want, and now the means without impacting my savings to have one. Also pay yourself first by ensuring your savings take priority over your bills. Of course, this requires discipline. If you live paycheck to paycheck, you probably need to reevaluate your spending habits.
I was lucky to grow up with a bad example of how to manage money by watching my parents go through many boom/bust cycles. Growing up poor due to mismanagement of money makes you not want to be poor as an adult, so I simply didn't follow in their footsteps.
To this day, they still mismanage their money and my mother will end up having to work until she dies.
I don't want that.
Start early, maximize, simplify. That's basically my strategy. Sure, there are some that find magical ways of making 30%/year, but that's not me. I'm content with standard market growth in my simple portfolio. I am going to look into investing in real estate now as well.