What should I do when I've spent the original amount I loaded on my card?

In most cases, you can simply add more money to your card. You can reload at your financial institution, through direct deposit of your wages, online or at any ReadyLink merchant.
You will want to keep your card — even after the balance is depleted and you decide not to add additional money to it — in case you need to return any purchased items. You might be asked to present the card when returning items purchased with the card.