Create Virtual Gift Vouchers

I want to design and attach virtual Gift Vouchers to my customer emails, and I need a way to record them and validate them. Initially, I want to send a $25 Gift Voucher to my entire email list, attached to automated mailouts, to generate extra sales, and later I want to send out a couple more ‘$25 Off Your Next Order’ Gift Vouchers with each order (one for you and one for a friend), but with the condition that in order to activate the new voucher, the customer first has to take a photo on their phone of my product, then post it to our Facebook or Pinterest page, and then ‘Like’ it. I would very much like all this to be automated where possible, which probably means a form of electronic serial numbers and a database to keep a record of everything. It will also require that postings to Facebook/Pinterest are logged. I will need several different Gift Vouchers of different values, which can only be redeemed within a certain period against a future transaction of a minimum value. If you can help please contact me with your ideas. Please try to keep it simple. My budget for this is about AUD$60. Thanks.