What I would recommend doing is only run 1 or 2 a day at first. If you are new and dont plan to whale early on, just evolve your silvers first. while you will not be getting strong very fast, as long as you can complete E-8 and gt the gems, you do not have to worry. At my current time, event dragons outnumber the number of girls I get so do not stress about it too much.
I understand btw that you probably cannot do E-8 yet, but you have to ask yourself if the daily missions are really worth the stamina cost...