1. You cannot buy Obamacare. It is not an insurance policy, it is a set of regulations for health insurance providers.
2. If you do not have your own health insurance, and do not qualify for the expanded Medicaid coverage (probably because your state has refused to accept it), and do not choose to buy some from the exchanges (even though you would be given subsidies to help you purchase it), then you will be fined $95 the first year.
3. No one is going to jail. No agency has the authority to make that happen. The only enforcement or punishment for not paying the fine would be having it garnished from any tax refund you might receive.