is it important to "complete daily quest" in terms of long term investment value?

Not that much. You basically get a $2 worth Booster Pack for winning 10 matches with a specific type (Fire, Water etc.) You can go to the official website and read more about it. Winning daily quests would eventually get you ranked higher in leagues which would also get you some prices. If you have few thousand dollars to invest, daily quest doesn't mean much at all.