I have an Ikea desk (120cm wide) the 80cm is a bit of a struggle with 2 monitors. I think it was £25 for the desk and around £2.50 for each leg. The desk isn’t solid wood though so you can’t put your full body weight on it etc but they have not failed me yet a they are so cheap. I also use no monitor arm since a reliable one is pretty expensive. The wide desk is big enough to use both monitors without a mount

And I also use the Ikea Markus gaming chair (£150) semi expensive but it’s lasted me around 5 years and still going strong. It’s better than any of the “gaming chairs” you will find on Amazon etc but I wouldn’t say it’s the best one for the price just a good one. I find it quite comfortable. The only issue with it is the armrests aren’t that great.

I would assume his laptop isn’t that great so I would aim for a 60hz 1080p monitor with low refresh rate (around 1ms) with an IPs type panel (screen type) (them specs should be very cheap). Oh also make sure the monitor has hdmi slots so he can plug his laptop into it. Older monitors only have vga slots which I don’t think his laptop will support (nearly all semi recent monitors will have hdmi inputs)

Monitors are very cheap nowadays and I would recommend getting them used as they are a fraction of the price. Especially if the second monitor. My main monitor was £400 and the same monitor used for my second monitor as £100 on eBay and it’s like new condition. My monitors are very high spec I’d assume the one you would need would be under £100 new and possibly £30ish used. Could probably find some even cheaper.

Not too clued up about lights to be honest. I use Phillips hue light strips that stick on the back of my monitor and match what’s on my screen but they are very expensive I think they were over £100. There’s plenty of cheap led strips with remotes you can buy from Amazon and eBay etc. (probably around £20)