Rules of getting best audio ? maybe..

I have just started the hifi audio journey since about a year or so and have learnt a great deal. I am sure many of you here have much more experience in this arena and have gone through your journey. Some mistakes made, lesson learnt, but still it is ongoing journey.
I have set up my stereo as well as home theater, spent great deal of money and have learnt some valuable lessons and thought of setting up some guidelines/rules, so that if I could go back in time, I wish I had these steps in mind and followed these "rules" instead of doing costly trial and errors. 
These are my rules for my past, if I had to start all over: Hopefully this might help someone who is about to start. 
1. Buy the equipment you think is the best for "your ears" and not the second best, even if it is a little bit expensive compared to your budget, but within reasonable margin: this will prevent you from regretting and trying to sell the second best equipment you brought for significant loss, to go back and buy your best. We all know that in this journey "the law of diminishing returns" are real and costly. 2. On the other hand, just because the equipment is expensive, does not mean that they are necessarily best option for your ears. Something cheaper (less expensive, I mean) can be the best for your system and your ears.
3. Just because you are getting something for very cheap, does not mean it is a good deal: They are cheap for a reason.
4. Cables do make a big difference in quality of hifi. You don't have to be a "believer": you will hear those difference, if you audition them. 
5. Add a good subwoofer to any stereo set up (full range speakers or not): They make you mids and highs shine like diamond. 
6. Spend some time and money to set up room acoustics, consider room size, before you decide on how big your system will be. 
7. There is no quantitative metric to measure "qualitative" fun. Trust your ears and your ears only. Pay attention to good reviews but don't rely solely and only on "reviewers" ears.
8. All said, in the end, it is "your ears" " your wallet" and "your music". Use it and enjoy it wisely. Work hard and play hard. 

Share your "mistakes" and "lesson learnt" moments if you agree: if you don't agree, ignore this and don't trash please. Constructive criticisms are always fun though.