The Ravnica block is a pretty well-known and large one in the Magic The Gathering game. This block all started with the expansion called "Ravnica: City of Guilds" to which the "Selesnya United" themed deck belongs.
The cards in this deck are either white or green. This deck offers 3 ways in which you can win a challenge. This shouldn't stop you from adding or swapping cards you might find as a better choice, to give you more and improved winning solutions.
Before you go ahead and swap out the Scion of the Wild and Tolsimir Wolfblood, remember that these cards are rare and thus you might want to keep them.
Here's how the cards are broken down, based on what they show: