mug punter

noun

1. slang.
   a customer or client who is gullible and easily swindled

Example Sentences

Take the case of the self-confessed mug punter who backed England to win the Euros at 16-1, sees them now backed in to 10-1, and is thus labouring under the delusion that he has what the betting community calls without a hint of irony "a value bet".

From The Guardian

The unpredictability of the course makes it a field day for the mug punter, as was the case last year when 100-1 shot Mon Mome pulled off a shock victory.

From The Guardian