Referral Candy & Affiliate

One week in, so far it seems to be the best option for the cost.

Pros: visibility of data & customers, good support (chat available), syncs with MailChimp and ReCharge (subscriptions), links don't expire, URL is customizable.

Cons: No ability to use gift cards as a reward (more of a Shopify issue I believe), the referral discounts list individually in Shopify so it completely trashes your discount list (you can't just scroll and review discounts anymore, which is crazy cause other systems can group them under 1 discount), it's on you to display what your referral restrictions are, if you say Min of $30, there is no automation to build that into the emails, you have to go type it all.