With a miter saw and a drill.... Let me make a few tool suggestions (I'll keep them cheap) and an idea for a decent bench.

This hand saw

It's an absolute beast. And I love mine. I often use it for crosscutting 1-2 2x4's even though I have a sliding miter as well. (if I'm doing more than 2 cuts, though... the miter saw is the way to go, it is faster, but it's noisier, and creates more dust... there are trade-offs)

But I can't easily cut a corner notch in a piece of plywood with my miter saw.

In terms of bench. The big box stores sell quarter sheets (2' x 4') half sheets of plywood (4' x 4') or full sheets (4' x 8'), and they'll cut them down (but accuracy may be sketchy here)

So with a need for a 4' long bench, that you can move I would suggest buying a few 3/4" sheets of the quarter sheet plywood so you can use them as a top. Just glue them together so you have a nice thick surface. 4 sheets would make for a 3" thick top (it'd also be a bit heavy so maybe some casters are in order)

But with a 4 foot long bench, you could build the legs/frame/bottom shelf/etc out of cheap 2x4 stock using the mitersaw, double up the leg thickness so you get a nice beefy structure, and you can make some faux half-lap joints by layering the 2x4's for a very strong base. Get another sheet of the ply for a shelf under the bench where you can use for storage of tools or projects or both. (you'll need to notch the corners here to fit around the legs, or you'll have weird gaps around the shelf)

Maybe you need a larger top, but you can adjust that as needed, you'll just have to figure out how to get the plywood top cut to size... alternatively you could use the laminated 2x4 method but then you have to figure out how to get that surface flat, and unless you own a table saw, or lunchbox style planer, or a bigass smoothing plane (although surfacing that by hand would be a fucking workout) But getting the 2x4's to size for the top would be well within your wheelhouse with the miter saw.

Mind you this is coming from a woodworking perspective so your needs for a thick/flat top may be different, and you can obviously adjust those to better fit your use case. But a solid workbench is one of the more useful tools in a good shop. And it's easier to build it well the first time around than it is to retrofit in the stuff you wished you'd thought of later.