There are lots of different carp baits on the market these days. However one bait that is very cheap is grilled bacon ends.
I have used this on many occasions with great success. I think its because carp get used to luncheon meat, corn, boilies and pellets, so when a semi rare bait is introduced they jump on it immediately as they do not associate it with them being caught.
As a tip, try soaking it with soya sauce overnight.