Back in the day, tables were the standard. Now, the majority of scuba divers dive with a personal dive computer and they should.
Your computer monitors depth, bottom time, ascent rate, and no-deco limits in real time. Dive tables are a fixed calculation. When you move between depths during a dive, a computer adjusts. Tables don't.
Watch-style computers are the most common buy at this point. They're small enough, readable underwater, and you can wear them as a daily watch too. Console models are still around but fewer divers choose them now.
Budget computers start around $300-odd and do everything most divers requires. They give you depth tracking, dive time, no-deco limits, dive logging, and often a basic apnea mode. Mid-range adds transmitter compatibility, nicer displays, and additional mix modes.
What new divers overlook is conservatism settings. Some algorithms are tighter than others. A tighter algorithm means reduced bottom time. More aggressive ones give more bottom time but at reduced buffer. It's not right or wrong. It's personal preference and how experienced you are.
Check with people at a Cairns dive shop who dives with a best dive computers few different models before buying. Good dive stores will give you a straight answer on which ones hold up versus what's marketing. The better Cairns dive stores put out product guides and honest reviews on their websites as well