Agree on the duct tape. Not a fan of it for “permanent” repairs, but it can be a great temporary fix to get you to a better place.
Also big fan of tire plug kits and a portable compressor. I went through a spell where I picked up nails regularly. I assume someone hauling construction scrap was using the same route to work as me. Anyhow, it got to the point that I could plug a tire and reinflate it faster than I could have hauled out the jack and spare and changed it. Keep a garbage bag or some cardboard so you can lay on the ground if you’re in nice clothes or it’s raining.
It’s also wise to be familiar with your vehicle. Plenty of message boards out there that are car-specific. Find out what is a common problem and either fix it before it breaks or have the means to fix it on the go.
I’ve learned to hate in-tank fuel pumps. They generally go without warning, and then you’re stranded. Worse, you can’t fix them without dropping the tank. On every pickup I own, I cut a hole in the bed and put in a marine hatch right above the fuel tank access. Then, with a spare fuel pump, I at least have a chance to get myself back on the road if/when it dies, and I can change them out regularly with some ease. Not always practical to do in cars unfortunately as the tank is generally under the back seat.
A can of WD 40 for things that are stuck and ain’t supposed to be and a roll of duct tape for things that ain’t stuck what’s supposed to be. Hat tip to Red Green.
I too went through a spell of flat tires and the Fix-a-Flat just doesn’t cut it. I wish I had a tire plug kit. I’ve got the compressor.
Basic tools are also a must.
I was able to replace my serpentine belt and the burned out pulley on the side of the road in 45 minutes. That included calling a cab to get to an auto parts store and back.
And even more basic.
A paperclip.
I’ve hot wired my own car at least three times when the keys were lost or the ignition broke with just a paperclip. Not to mention the vehicles I didn’t own.