I would rather not teach anyone but if they insist, you inform them about the implications and the addiction problem.
I would also advise against teaching gambling to under age people . I believe they can be easily affected by gambling problems.
Its not good to influence people to gamble, and if they insist you must tell them everything about gambling. Teenager are easily to influence, they should be guided by the right gambler or person so they can be prevented. Lets not encourage everyone to gamble, we know its risky.
We need to stop considering gambling as a sin,it can be a great entertainment when we know how to use it,so teaching them about how you need to gamble and why you need to gamble will help.