>Recommend me a decent PC microphone that costs about a tenner.
A Boya BY-M1 lavalier for £15 will do the job for video conferencing, gaming or casual YouTube stuff. It's an analog microphone, so you're totally at the mercy of the microphone input on your soundcard; that may well be complete crap, particularly if you're using a laptop.
The cheapest microphones I'd recommend for serious recording are the Samson Meteor or Blue Snowball iCE, both of which cost about £50.
It's been mentioned elsewhere on this site that a USB microphone will cut out signal noise but I've noticed there's an irritating latency with mine, that I discovered when trying to turn my computer into a karaoke machine. It depends, then, on what you're looking for; if it's for video chat or teamspeak, I'd go with a cheapo analogue one. If you're looking to do voice-over our audio blogging on a budget, go with USB.
I can't imagine there's anyone who uses .gs who's sampled a wide range of budget microphones. I think you might have to pop down Maplins and just buy whatever cheapest mic they have and hope it's good.
All computer-based audio has some amount of latency, due to the conversion from analogue to digital and back. An analogue microphone plugged into an ordinary soundcard is likely to have particularly high latency, because soundcards aren't optimised for recording applications. Windows isn't really designed for low-latency audio, so you need to use special ASIO drivers and compatible software to achieve un-noticeably low latency with either a USB microphone or a dedicated audio interface.
Whatever the application you're using the microphone for, you can make a massive improvement to the quality of the recording, just using a few improvised tricks like stockings over a clothes hanger to make a pop-shield, and some towels hung behind you to deaden echoes.