I agree with the advice of all the other commentators, but I'll add a recommendation to have a few Irwin Quick Grip clamps on-hand (or similar). They're my go-to for 90% of just holding something in place for a moment (e.g. when drilling a hole with two pieces aligned).

You want a good pair of parallel clamps or pipe clamps too, for when gluing stuff, which can hold something precisely for a long time with a lot of pressure, but most of the time, you want something fast.

I also recommend a few clutch-style bar clamps, since a lot of time, you're reaching over something.