Spare tube: Sometimes, a tube is just too damaged to be patched, or has had a failure such as the valve stem breaking off which isn’t something that can be patched. To save weight and space, I usually keep a lightweight version of the right size tube for my bike. Since one of the first things I do with most bikes that I own is switch them over to heavy-duty thorn resistant tubes, I just take one of the originals and put that in the toolkit.
Next, two-stage designs. There are two types of hand pump. HV (high-volume) pumps, ones that pump a lot of air but don’t have a lot of pressure, which are used for mountain bikes. The Lezyne Alloy Drive is a high-volume pump. Then there are HP (high-pressure) pumps, which pump a small amount of air but can inflate to very high pressures and are used on road bikes. Our top pick is a high-pressure pump.
Modern bottom brackets use a sealed bearing type construction that keeps water and debris locked out, so they seldom go wrong. Maintenance is impossible so they need replacing when they do wear out. Older style cup bottom brackets need to be re-greased every now and again, and occasionally will need to have their bearings replaced. There are a lot more teeth on the chainring cogs than those on the rear cassette, so need changing less regularly. Cranks usually a solid one piece construction so there is not much to go wrong.