If you have never tried any of this: a small set, not a ten piece. Three or four pieces tells you what you actually like. A big kit mostly tells you which seven things you will never use again.
If you are buying it to start a conversation: buy for how it looks. A pastel or satin set is far easier to put on a bed than black faux leather and hardware, and on the first night that matters more than the contents.
If you already know cuffs are the part you want: check the closure before the price. Adjustable buckles or wide hook and loop fit a real range of wrists. Fixed sizing is the single most common reason a kit gets abandoned.
If you live somewhere with thin walls: fabric and satin over metal hardware. Clips and chain are louder than anybody expects them to be.
On safety: agree on a word before anything goes on, and keep scissors within reach. Never leave someone restrained on their own, and check hands and feet for cold or numbness rather than waiting to be told about it.
If you would rather read first: our BDSM starter kit guide walks through what is worth buying and what is not.