I can't imagine a buying a GPS is going to save you much money long term versus using your iPhone. How much data are you actually using a month with your GPS? How much are you going to save a month reducing that data?
Plus you're giving up a lot to get a GPS- you have another device to carry, charge and honestly, cheap ones won't come close to matching the features on your smartphone. Right now, if you see a place you like on Yelp or Google, it's two clicks to start navigating there, or even fewer if you're asking Google Voice to navigate somewhere. With a separate gps, you'd have to pull out the damn thing, turn it on, wait for it to boot, navigate an interface that's usually clunky and incomplete, probably plug in the street address manually on a keyboard that works as well as marshmallows and pray it works. Standalone GPS's also don't get regular map updates and frequently force you to pay for them.
Give up on buying another GPS.
