This advice is GENERIC advice on how to build a stereo system FROM THE GROUND UP. Should work in most cases, but may not cover all outlier situations, highly unusual approaches & expectations.
Step 0. Room
Take care of your room, and equipment setup. If this is not done, even the "best" audio gear will give you highly limited results. Just remember: to drive a race car you need a race track, not a corn field. Same goes for audio, not just recorded, but live performances as well: we don't listen to a symphony in a pub or in a printing press.
You need not scramble for acoustic panels and bass traps in the beginning - that's just a last resort. Be practical, use your available resources (furniture, furniture placement, rugs, bookshelves etc) first. You might have everything already, just need to rearrange and find optimal loudspeaker position. More / deeper advice would take the form of many books. Educate yourself, and TRY out the things you read about, don't just hoard them as (otherwise useless) mnemonic boat anchors.
GOLD ADVICE: if you have a compromised room NOW, then keep in mind to plan for an optimal room when you MOVE. Factor in optimal stereo setup at your next house / apartment choice. (THIS IS WHAT I DID! Plan, and be prepared to build your room from ground zero.)
Step 1. Commitment (& Speakers)
Make sure you have the right loudspeakers to match your room, preferences, and YOUR AUDIO PATH. Mainstream or Purist.
Two kinds of loudspeakers: 1. High efficiency & Easy to drive and 2. Current hungry requiring an arc welder. By picking one, you pick your AUDIO PATH. (Purist VS Mainstream). Not choosing a dedicated path, and just aimlessly switching between random amplifiers and systems approaches IS the road to Audio Hell. At this early stage of system building, just get a decent amplifier to MATCH the loudspeaker philosophy and you are fine.
Step 2. Source
Get a good source. Without a balanced source, you might skew your system to compensate for the weaknesses of the source. Digital: CD as source is a solid start, streamers can be a total bust even at extreme prices. Analogue: ground zero is a good table & arm & MM cartridge & phono stage combo. A huge error with vinyl is to get a good table and a weak phono stage.
Step 3. Wires
Interconnects!! As you have a good source, now it's time to hear more of what it does. Start the upgrades at lowest signal level. (Eg turntable - phono stage first, preamp-amp last).
Step 4. Amp
Optimize your amplifier. Maybe it needs only tweaking... or you need a major upgrade. Whatever the case, now you are ready to appreciate it. It's also time for upgrading / optimizing speaker cables, and power cords.
Step 5. Preamp
High quality VOLUME CONTROL. (AVC / TVC, or even better: absolute hot rod, no volume adjustment, just let it fly at your optimal listening volume at all times!) Fixing this will result in a paradigm shift and totally change how you listen to music, and what you get out of it.
Step 6. Tweak
Taking optimization further - now you are ready to go for MC cartridges, or go for high level digital sources. Go for next step in cabling. Research TWEAKS. This is the point where tweaks will be accessible for you: their purpose is fine tuning, and will work only when there's opportunity to fine tune (opposed to having major issues that need a MAJOR OVERHAUL, not a simple / little "TWEAK").
FINAL ADVICE:
Do not start from the top!! The worst service you could do to yourself is to get a "million dollar system" as your first system. Start from lower / intermediate level, and climb higher. It's not just your system evolving: your HEARING SKILLS NEED TO STEP THE F@&# UP in a MONUMENTAL WAY.
While we all have the same biology as ears, it's ENTIRELY up to our TRAINING AND EDUCATION of how much of the perceived information is CONSCIOUS. It's not the earlobes that make the difference in hearing, it's YOUR hyper-complex NEURONAL PROCESSOR CALLED YOUR BRAIN. Observing spatial cues, distortion in the sound, harmonic content, frequency range, soft passages, shot AND long term AURAL MEMORY - this ALL ENTIRELY depends on your TRAINING, and ranges from flat tire to Mozart.
Without a TRAINED BRAIN a high level audio system is a COLOSSAL WASTE, as you are unable to judge it for yourself, you will seek other's validation on how it sounds... With trained ears a very refined system will impact you a thousand fold, and you can tell for yourself whether you are hearing something special, or was it special only for the bank account that paid for it.
Analogy: to an untrained individual an intermediate boxer and a high level boxer seem the same: both knocks out a clueless dude in two seconds... however, to a good boxer, watching high level boxing is a true treat while watching an intermediate fellow is often cringe-worthy. As in every other area of life, so in audio, TRAINING IS EVERYTHING when it comes to QUALITY OF EXPERIENCE.