The cheapest car insurance, period, will likely carry the minimum coverage required in your state. In most states, this is liability insurance only, which covers property damage and medical bills for others due to accidents you cause. Some states also require uninsured and underinsured motorist coverage, which pay for your injuries or damage if an at-fault driver doesn’t have enough insurance.
Collision coverage is limited to the actual cash value of the vehicle, and requires a deductible, which is the amount you'll need to pay before receiving benefits. Higher deductibles lower your premium but increase the amount you must pay out of your own pocket if a loss occurs. Ask yourself how much you would be willing to pay on short notice in order to save on your premium, or talk to your agent.
In the states with no-fault insurance, insured drivers are typically paid for medical expenses by their own insurers, regardless of who caused the accident. Nonetheless, BI liability coverage is still required in no-fault states because if injuries are bad, the at-fault driver may be sued by the injured party. If that happens, your BI coverage can help cover your liability expenses.