What to do if my father died intestate but his wife has taken everything they owned and has given me nothing?

You wouldn't be entitled to anything if all of the property was held in joint tenancy or was community property, as the right of survivorship applies in favor of the surviving spouse, or he could have willed his whole estate to her. You need to check this out before you go forward. If you decide to go forward against your step mother?? then you should seek the assistance of probate counsel.