How to not use all my data iPhone 5?

I got an iPhone recently and my dad says its an "experiment" I get 2G of data and I've had the phone for 5 days and have already used.5G. So I'm freaking out because if I go over my data, not only will it cost a lot of money, but I'll have to give up my iPhone. So what can I do to limit data usage?

What you can do is upgrade to unlimited data. I don't see why you wouldnt do that.having a limit on data is risky and your cell phone will use data even when its sleeping.

Avoid videos. That is a lot of data that you can cut out really easily.

Don't use anything that has to load. You can play games and text all you want and not use data. Use Internet stuff when on Wi-Fi.

Avoid videos or only do that on Wi-Fi.