A cluttered desk usually isn't the result of one bad decision, it's the result of a dozen small ones made over months. The fix isn't a single big purchase, it's picking the right order to solve problems in.
Start with what you touch most
If you use a laptop, that's a stand. If you're on calls, that's a headphone stand so they're not tangled in a drawer. Solve the accessory tied to your most frequent task first.
Then solve what you see most
A desk mat or pad does more for how a desk looks than almost anything else, because it defines the entire surface. It's also one of the cheaper upgrades in most setups.
Then solve what you're tripping over
Cable trays and organizers come next — not because they matter less, but because you now know exactly which cables and items you actually kept, instead of organizing clutter you're about to get rid of anyway.
Add lighting last
A monitor light bar or desk lamp is the finishing touch once the rest of the surface is settled, since it's meant to complement a setup, not fix a messy one.