Just chuck the free Allen keys from flat packs and buy a single set to keep in the toolbox.
Also buy a cordless screwdriver doodad with a set of Allen key fittings and heads, makes making flat packs a doddle.
Actually a really good toolbox with the right small tools, properly looked after, and tool cupboard with all the little things in pots and labelled, so you can quickly find cable clips or something and attend to 2-minute jobs in two minutes. And also not buy cable clips over and over again. Sometimes Ikea gives you extra dowels: save those to plug wall holes before filling, or for little DIY bits. I use old yoghurt pots and a whiteboard marker, no need to buy a label maker or boxes. Label maker = extra thing to store!
Also chuck the instruction manuals from everything and Google what you need when you need it.
Find what works for you: I find it quicker to scrawl “curry” on my whiteboard than I would to make visual magnets, store a hot glue gun, print and laminate pics etc, and also I want less stuff in the house not more. And I dream of the day I live alone and won’t need to meal plan and can throw out the whiteboard! For me, the more I throw out (tip, recycle, Olio etc), the easier life becomes. Same with the document pouches upthread to save sticking an address over reused Jiffy bags – since I’ve got sellotape in the house anyway and an endless supply of paper (there’s always a letter or circular about something, or the back of an envelope), it’s quicker (for me!) to use those and one less thing (the pouches) to find a home for. As with the label maker: I just use pens, possibly some washi tape if needed. Use what you have! Always declutter ruthlessly before buying storage!
I organise the medicine cabinet this way too, so painkillers, hay fever, cold remedies, bums and tums, etc, and keep the kids’ red books in there too, because logical. A friend has all her household medication in a giant plastic bowl like outside the greengrocer, so you need to rummage; it makes me clench at the chaos!
Paper: I never buy notepads for shopping lists, keeping track of DC calpol/nurofen when they’re poorly and need it endlessly, quick on-the-day to-do lists. Every time we get a letter that’s blank on the back, tear it in four and shove it in the bulldog clip on the fridge. Free notepad!
Now all I need to do is get DP on board with the “buy less” ethos. The man has 102 T-shirts and has yet to grasp this causes more washing, not less…