I think I need to replace my cheap gauges with some better ones. I'm not convinced they are reading properly.

Boost gauge seems fine but the oil temp and oil pressure ones seem a bit hit-and-miss.

 

What gauges are recommended? I'm not wanting to spend a fortune, just get something a bit more reliable.

I'd look at the senders, how and where they are positioned first. Could be there's a kink or obstruction for the pressure one, the temp may be slightly out of the flow or the adapter has a cools it down?

How about a OBD2 Bluetooth Plug in and a Phone App?

 

http://auto-polar.com/index-load-Polar_Fis_adv.htm