Hi Dave, the coin and relic market is awash with great multi frequency detectors. The Nox 800/900 is a proven performer as are the Nokta Legend and XP Deus I andI II . They all have very similar performance, so things like price, durability, ergonomics and features should be factored in to any purchasing decision .
There are lower spec models from both Minelab and Nokta which can get you started for a reduced outlay too. Plenty of choice out there.
From my personal perspective, I believe of the three that I’ve mentioned, the Nokta Legend stands out as being the best value for money and durable waterproof machine you will find. Although it’s user interface can be a challenge for newbies.
A good tip on buying for the first time is to look for package deals on offer as the competition for sales is pretty high.