Tbh if your a bit of an introvert clubs probably wont be your thing.
Anyway for me in Birmingham....
Mega cheap night. Bus in (child fare), 3 pints, find girl and get her to pay for taxi back to yours. £6
Cheap night. Bus in, £10 with 10 free drinks, bus out. £11.80.
Average night. Bus in, £20-30 on clubs, food, shared taxi home. £35
Stupid night. A couple of times year over £100.