Opening Reward Cards

Today I was lucky to get an epic dragon card which called Manticore. Till now I never got this card from opening reward cards. I also got Naga Fire Wizard and Silvershield Archers which are great cards. I always try to not miss daily quest to open reward cards with excitement because you neve now what you'll get maybe a gold foil legendary or just a 2 cent worth of common card. I don't know if l should sell this card to buy another regular cards or buy a dragon summoner to use this card. One of the disadvantage of playing with dragon cards is that you can't do daily quests with them but if you want to rank up then this cards can be a good option for you.