I found a debit card and used it for gas and paid a bill in cailforinA

You certainly could be charged with a felony and sent to jail, but nobody can predict whether that WILL happen. Don't talk to anyone except an attorney about this incident, and don't post additional details on the Internet. If contacted by police or arrested, politely say, " know I have the right to remain silent and I'm not answering any questions without a lawyer."

I would suggest that you not post any further details about this on a public forum. Have criminal charges been filed against you? If so, I would recommend that you consult with a criminal defense attorney as soon as possible.

Jail is possibility, but at this point it's not clear that anybody, particularly law enforcement, even knows about this. Quit make admissions on public forums. Don't use the card again. QUIT STEALING.

Are you going to jail? It's possible but can't make that prediction. It appears from your description that police or the owner of the debit card are not yet even aware of of the purchases. Do not post any further incriminating statements on a public forum. If you are contacted by police, do not make any statements without first consulting with a local criminal attorney. Finally, stop stealing and using debit cards that don't belong to you.