Hi Kildavin,
Quite the opposite, Revenue don't really believe in gambling profits, they have an assumption that you lose as much as you win. It's [broken link removed] if you scroll down to "sources of capital".
Obviously small gamblers from time to time do win big. I remember a woman who worked for Revenue in the papers a few years ago having won well over 100,000 on a small Yankee of about 5 euro but I'm sure if this happened to you then you would have evidence for when Revenue started asking how a person on an average wage managed to come up with that sort of lump sum.