Years ago, dive tables were how everyone dived. These days, nearly all scuba divers wear a personal dive computer and they should.
Your computer monitors your depth, bottom time, ascent rate, get more info and no-deco limits in the moment. Dive tables are a fixed calculation. When you move between depths mid-dive, a computer adjusts. A table can't.
Watch-style computers are the most common use now. These are small enough, readable underwater, and you'll use them as a daily watch as well. Console computers are available but less divers choose them these days.
Basic computers start around $300-odd and handle everything most divers needs. You get depth, bottom time, NDL, log function, and sometimes a simple freedive function. Stepping up to mid-range gets you transmitter compatibility, improved screens, and extra gas modes.
Something buyers forget is algorithm differences. Some algorithms are more conservative than others. A cautious setting results in shorter no-deco time. Looser ones give more bottom time but with less buffer. It's not right or wrong. It comes down to personal preference and your diving background.
Ask people at a dive shop who uses multiple brands first. Good dive stores will offer a straight answer on what's good and what's just marketing. Most good dive stores put out product guides and honest reviews on their sites too