The usual recommendation on how much medical malpractice to buy is to carry the same amount as other doctors of the same specialty in your geographic area. That usually varies anywhere from a few hundred thousand to a couple of million dollars. Policies are usually described as $1 million/$3 million, where the first number applies to the amount per case and the second number is the total amount the insurance company will pay out per year.
There are generally no deductibles with malpractice insurance. While it would be nice to get a policy where the doctor pays the first $10,000 and the insurance company picks up the rest, that's not the way these policies are written. They generally pay from the first dollar and then cap the payout at a certain amount.
Whether you should buy more than the average doctor in your area is an open area of debate. Some malpractice attorneys (both on the plaintiff and the defense side) have told me no. Others have told me yes. There does not seem to be any consensus.
Many doctors worry a larger policy just makes them “deep pockets” and more likely to be sued. Legal experts seem to agree that is not really a concern. The key seems to be to have “enough” that a policy limits payout is enough to satisfy both the plaintiff and their attorney. They want to feel like they got “a lot” of money. One million dollars still seems to be “a lot” of money, so that is probably the most common amount carried by doctors.