The Valentine Dragon in Dragon Story is a Pink/White type dragon that you can purchase in the market or craft. It is a Pink/White type dragon which means it will go onto the Pink/White type habitat and start gaining you coins with other Pink/White type dragons or hybrids.
If you want to evolve your dragon in Dragon Story then you need to level them to level 4 to evolve into the teen stage then level them to level 6 where he will need to use the evolution temple at the end of the level to evolve into their adult form. After this process you can evolve the dragon into his epic form when he reaches level 10. You cannot go beyond level in the game but you will see other dragons in the battle arena that are beyond level 10.