Add an achievement where you get rewards to getting certain levels/rank - for example rewards for getting rank 5 / rank 15 / rank 30 / rank 50 etc
Does Charizard have a chance to give Support candy? If not charizard should do that.
Support Pokemon Gengar - I have Gengar and honestly I'm slightly dissapointed for 600 gems, and I think he needs changing slightly.. I personally think from having Gengar that 10 hours for 1min and 30secs is more reasonable than 14hours for 1min, the Magikarp is kinda slow at eating and training, you don't get the effect from the Support Pokémon Gengar. Which is a shame for 600gems.
Make Magikarp eat slightly faster as well
Add a lucky Magikarp Wheel! - for example - win a chance to get coins, 12 pieces of food for the pond, support candy, items - spin the lucky wheel once a day. Add a brand new support Pokemon in the wheel - you can only get the support Pokemon from the wheel.
Add more achievements within the game! (One i have suggested)
Hope you like my suggestions! I hope the Magikarp creators will see this xD