I currently use a wrist mount Dive Rite Nitek Duo - it does air/nitrox and can do in water gas switching for deco gas mix also - simple to use, big easy to see numbers, will work from beginner through to some technical diving. Big plus is it’s relatively cheap (you can pick them up new for around $300 (or less). It’s also exactly the same computer as the Tusa IQ700 and the Zeagle N2ition and at least one other rebranded ’puter - apparently they’re all made by Seiko and put in a different mount by the "manufacturer"