State laws differ however in some states you need a license (or state ID) to register a vehicle and then in many states you need to provide proof of insurance when you register a vehicle. In most cases, you can purchase insurance before you reinstate your driver's license. However, your insurance company will most likely demand you provide proof your license has been reinstated within thirty days (30) of your policy's inception date, or they will cancel your policy.
You will need to check with the Department of Motor Vehicles of the state you reside in to find out if they will allow you to register a vehicle with a suspended driver's license. You also should check to see since you will be reinstating your license due to a DUI suspension if you will be required to file a SR-22 financial responsibility form as part of your reinstatement process. If so then you will need to find an insurer that will file this for you when you get your car insurance policy started on the car you buy.
Remember, you can click here to get a quote for auto insurance Texas (or any other state in the United States) to compare your rates.