Know what you are trying to do. What kind of music do you love? What kind of tech do you want? Is it just 2 channel or do you want theater?
Most of all, the room is the room. Understand it and what can and cannot work. There is plenty of empirical data - you can avoid a lot of problems by paying attention. This includes dimension, construction, power and WAF. These are immutable givens - addressing any of them is expensive.
Unless you live where home auditions are possible and you can afford it, buy used.
Learn how to listen- develop those skills.
understand that your tastes will evolve or morph and some assumptions may need to be re-examined.
Know that the point of diminishing returns is quickly reached- as the wise man sai, don’t let perfection be the enemy of the good. If you start with good stuff the third or fifth version may not be that much better.,,
Finally relax and take your time - a system is part of your life, not your dr focus- least it should be IMO.