erika: Since you are not an adult, you can not make any investments except a savings account which pays almost nothing for interest.
You have only two legal sources for money. Earn it or receive it as a gift. Drag out the lawn mower and go down the street looking for lawns that need mowing. Ask if they will pay you to mow the lawn. In about 8 Saturdays, you should have earned enough to buy a really nice lap top.
Learn how to mow lawns.