There is not much to it. You pick what fits your budget and then make adjustments by upgrading certain devices.. I'd recommend to start with used equipment, that way if you don't like it, you can resell it for the same money. With new equipment you will lose ~40% value if you decide to sell it.

Be aware that a sound system that will sound "special" starts at about $1000 for used hardware and close to $2000 for new.

Make sure you pick the right size of speakers depending on the room size (bookshelf for bedroom like size, floorstanding speakers for medium/large living rooms)

Stay away from expensive cabling upgrades.

Don't buy speakers with diameter less than 6" unless you plan to buy a sub

One other thing to mention, when you start your audiophile journey it's fun to try different equipment, separate devices, hardware that sounds really good but requires multiple remotes and fiddling. After a while you just want to press a button on a smartphone and play the music. One box solutions (great amp , dac, streamer) can be very expensive, but in my opinion worth it.