The battery is fine. With a new phone, you are using it heavily. New stuff to try, new apps to download, etc. That's human nature. I do the same thing when I get a new iToy.
But you will find that as your usage moderates toward "normal" the battery life will increase so that you can use it for at least a day before charging. (unless you are into heavy gaming, constant videos, etc.)
-If you use the phone frequently, it'll drain much quicker. Treat the battery like crap and it'll drain quickly and worsen the battery span/capacity.
-Turn off auto-brightness, lower the brightness
-Select Fetch instead of Push, then select either hourly or manual
-Turn off location services for apps you don't use regularly
-Turn off background refresh for apps you don't use regularly
-Turn off Siri
-Turn off Bluetooth
-Turn off Reduce Motion
-Turn off Automatic Downloads in iTunes/App Store
-LTE is a battery hog so turn that off if you need to prolong battery life
-Keep the battery north of 50% at all times
-Avoid bringing the battery to 0% unless it's for calibrating