I'm gonna get an s5 in August and I want to know about androids data usage. I have a limited data cap, and I wanna use my phone when at work. So how much data on average does the s5 use, in the background??
Most carriers have a data usage estimator tool. Try your carrier website for that.
Different things affect data use, as Almeuit said. There are lots of ways to decrease cellular data use. Some of the surest ways are to eliminate push notification on email, use WiFi as often as possible and sideload entertainment rather than streaming. You could also eliminate automatic backups to the cloud... Really the options are very numerous.