I think there’s a lot of great ideas in here, but I’d start with the stuff that, when you need it, you need it now.

Something I didn’t see mentioned yet was a wrench to turn your water off at the line that goes into your house. If you’re on a well, then whatever tools you’d need to turn that valve off. If you spring a bad leak you want to shut that off asap

A few other things that seem like good things to have BEFORE you need them

• Plunger and drain snake (Good to have both, sometime the plunger won’t cut it, but it’s much easier to use a plunger if that’s all you need)
• First aid kit
• Fire extinguisher
• Carbon monoxide/smoke detectors
• Spare keys, give them to people you trust or hide them really well so you don’t have to break in if you get locked out
• A big bucket for leaks, mopping, etc
• ladder
• Generator if you can afford it
• Emergency bag with food, water, flashlight, spare batteries, cheap phone, list of numbers, map, first aid kit, etc

Those are the kinds of things I’d look to buying first since anything else you can just go get when you need it.