It really depends who it is. I have two weddings this year, my cousins which is in a few weeks and a best friend of mine who's is in July, I don't see my cousin very much so I'll probably spend a little less on hers than one of my best friends. I think if it's someone you're not close to then anything from £30-50 is fine, then I'd spend £50+ for a close friends depending on how close we were..