Any Armani watch when second hand will cost a fraction of its purchase price because ultimately they're just cheap watches branded with an Armani logo. I wouldn't be surprised if it's Fossil that make them. Basically, don't think that a quartz Armani watch is an investment - you'll never get your money back.
If he's serious about wanting a decent auto for around £300, look at Seiko or Orient. Both offer in-house movements (watch internals) and have a good history in watch-making (Seiko more so than Orient).
The Seiko Cocktail Time SARB065 is a lovely dress watch with lovely detail on the dial that you won't get on a fashion watch. The Seiko SKX007 is a much-loved, bullet-proof diver which he might like.
Ultimately though, mate, if he's after an Armani, Michael Kors, Fossil, Skagen etc. etc., they're all much of a muchness and cater towards people who are more 'brand driven' rather than 'quality driven' You might find he gets into his watches a bit when he's older but in the short term, I'd be inclined to let him buy what he wants is he's not interested in a Seiko or similar brand.
Some excellent advice here. You should probably stay away from quartz fashion watches.
Your son may develop a deep passion for watches if you make a quality first purchase. I’d definitely recommend as a first timepiece a robust automatic mechanical watch from a reputed watch brand.
Can’t go wrong with Seiko. For a little bit more Hamilton is a superb Swiss watch brand that is respected by watch enthusiasts (as is Seiko).
A bullet proof first watch purchase with great resale is a Seiko Skx.
Or go for a Hamilton Khaki field if you want something a bit more military and smart on a strap. Also a bullet prooof first watch purchase.
Both of these pieces are iconic and been worn by famous movie and Tv stars. So great first choices.
If the budget is a bit tighter, for £125 the Seiko sea urchin / snzf is a great young mans first watch. It looks like the Rolex submariner. It has a see through case back too, which is a marvel for many people getting their first proper watch. You get to see all mechanical movement doing its thing. If he wears this for years, works hard and has a good career, I can bet this will be a gateway watch to buying a Rolex submariner one day (like fordy!)
All great choices that could start a love affair with watches. It’s a great pastime where you meet some lovely people, and a great geeky conversation subject at parties
nothing better than meeting a watch geek at a party! Lol ... Hope this helps.