Tables used to be the only option. Today, nearly all divers use a dive computer and it makes sense.
A dive computer monitors depth, time, ascent rate, and NDL in real-time. Dive tables are a fixed calculation. If you move between depths during a dive, a computer adjusts. Tables don't.
Wrist computers are what most people buy now. They're small enough, readable underwater, and you'll use them as a watch too. Hose-mounted computers are an option but less buyers go that way now.
Entry-level computers run about $300-odd and handle everything the average diver requires. You get depth, dive time, no-deco limits, a logbook, discover more and usually a basic freedive function. The $500-800 range includes wireless air monitoring, better screens, and extra gas compatibility.
Something buyers don't think about is algorithm differences. Some models are more conservative than others. A conservative setting means less no-deco time. More aggressive ones allow longer bottom time but at reduced buffer. Both work. It just what you're comfortable with and experience level.
Worth talking to people at a local dive store who uses a few different models before you decide. Staff will have honest opinions on what works versus what's just marketing. Most good dive stores have product guides and comparisons on their websites too