My Foal of Earth is Big Macintosh. This card corresponds to the Page of Pentacles in a normal deck, and represents the beginning of material and financial growth. Some may see him as slow and plodding, but not even tying a house to him will slow him down in the slightest, and he will persevere through even the most difficult of challenges without even a whisper of complaint. Also representing the beginnings of sexual awakening - the first blush of a meeting a new romantic partner for the first time, he is always the “perfect Somepony Special”, if the main thing you are looking for is deep feelings and long periods of gazing at each other in bliss.
 
With the other foals being the Cutie Mark Crusaders, I may change this to be Babs if I can figure out an angle, but for now Big Macintosh has always felt like the right fit for this card.