No questions about tax can be answered in an informed manner without knowing your jurisdiction. In the US, both federal and state laws would apply, and the primary issue would be income tax. To pay income tax, you need income. Casinos in the US report your winnings directly to the IRS if over a certain amount, but few individuals self-report their smaller winnings. In fact most gamblers would have losses greater than their wins - to claim that you are a gambling loser for the year would require you keeping your own records that an IRS auditor would believe though. You can take a clue what the tax man expects from what happens when you win $100 cash on the blackjack table or a lottery scratch-off, vs win the big lottery jackpot.

The gubmint would probably like you to pay sales tax on everything you buy off Craigslist or barter in exchange too. When businesses sell locally on the internet in the US, state sales tax laws apply. If government doesn't take bitcoins for taxes, how do they take 8% of the purchase price in bitcoins from a business, and what if the price of Bitcoin is 500% higher at the end of the year?

Estate tax? My heirs get a private key, they send what to the government?

The best way is typically to think of all of your bitcoin contact as a "sole proprietorship", taxable income only when you earn government currency gains. Your tax accountant would be the one to talk to, not bitcointalk.