Add 1 rule with at least 2 products in it. If the customer buys the 2 items (Minimum Quantity), they will get 25% both items (Reward).
In this next example we will demonstrate how to set up a buy one at full price and recieve a second item 25% off.
Add 2 rules. The first rule will have no reward. The second rule will have a reward of 25%. Thus, the 25% off will only be applied to the second rule.
In this example, the customer would need to add three items from Rule 1 to recieve $45 off their total.