Quick answer: In 30 minutes: offload unused apps (Settings → General → iPhone Storage), clear old screenshots and duplicates in Photos, close all Safari tabs, delete empty or outdated notes, and empty the Downloads folder in Files.
You don't need a whole weekend. Thirty focused minutes clears most of the clutter on a typical iPhone. Set a timer, work through these five blocks in order, and stop when the timer does.
Minutes 0–5: Apps
Go to Settings, then General, then iPhone Storage. You'll see every app with when you last used it. Delete anything you haven't opened in months. If you're unsure, choose Offload App, which removes the app but keeps its data, so reinstalling brings everything back.
Minutes 5–15: Screenshots and duplicates
Open Photos and find the Screenshots collection. Most screenshots were useful for a day and are clutter now. Select and delete in bulk. Then check the Duplicates collection under Utilities, where iPhone finds identical photos and lets you merge them. Don't forget to empty Recently Deleted if you need the space now. The full camera roll cleanup goes further if you have time later.
Minutes 15–20: Safari tabs
Touch and hold the tabs button in Safari and choose Close All Tabs. Before you do, save the two or three you still need. Then, in Safari's settings, set Close Tabs to close automatically after a week or a month so they never pile up again. Why we hoard tabs, and how to stop.
Minutes 20–25: Notes
Sort by date and skim the oldest notes. Delete the empty ones, the one-word ones, and the shopping lists from last spring. If two notes cover the same topic, copy one into the other and delete the spare. Don't try to build a folder system now. Deleting is the win.
Minutes 25–30: Files and Downloads
Open Files, then the Downloads folder. It's usually full of PDFs you opened once. Keep the ones that matter, rename them so they make sense, and delete the rest.
Keep it from coming back
Clutter returns because there's no obvious place for "stuff I might need later," so it lands as a screenshot, an open tab, a random note, a download. Give it one home. Snugit takes anything from the share sheet in one tap and makes it searchable, so the next wifi password or PDF doesn't end up as clutter in the first place.
Get Snugit and give the things you save one tidy place to live.