This is a progression based game. What you are asking for - is the repeatable quest on the “boat”. It’s technically enough to spin the grindwheel. If you are struggling with these repetitive quests… I honestly have no idea what to suggest, that should be physically impossible.
But if you just find the rewards lacking - consider using Automatch+Autocast(two taps in the upper right part of the screen) to just “farm” these quests without spending time manually.
Also, there IS basically a content void between levels 5 and 16, during which you’d be very lucky to finish Tundra, and it seems like you aren’t. So farm repeatables until you get 16, hopefully while trying to manage resources and upgrade dragons - and you might yet continue.