Yes. Your card can be used more than once*. If you need to buy different types of tickets (e.g. an adult and a child single, or multiples of the same ticket that would take you over the £30 limit), you can buy these separately using your card for each transaction.
The maximum number of tickets sold at any point of boarding is 3 or the number of people travelling (including card holder).
*Cards can only be used once when using Stagecoach Greater Manchester services