The amount of life insurance you buy will depend on how much you need, what you can afford to spend, and how much life insurance you already own.
Usually, life insurers limit the amount of coverage you can buy to 20 times your annual income. So, if you earn $50,000 per year, you may be able to purchase up to $1,000,000 of life insurance.
However, that depends on how much life insurance you already own, because insurers don't want you to be over-insured which may indicate someone is looking to buy life insurance to leave to their family and then end their life - there is an exclusion for suicide in life insurance policies within the first two years you are insured, one year in some states.
It's a good idea to use a life insurance calculator to determine how much life insurance you really need.