*Of course, there's one equipment that you're better-off buying as "brand new" or buy the more expensive [but trusted] brand 'coz your life depends on it. That equipment is the hose & regulators attached to your scuba tank & floating device.

Indeed, you have to invest some $$$ on the hoses & regulators 'coz it's your life's at stake. (It's extremely dangerous & foolish to use faulty hoses & regulators!) As for the tank, you can simply buy a used tank since they get inspected anyway by any dive shop before re-filling. If the shops don't re-fill it 'coz it's no good, then you can simply return it & look for another cheap tank.

As for the rest of the gears, you can simply buy the cheap ones since they serve the same purpose.