How much MB will I need for an iphone?

I'm getting an iphone 5 and i'm not sure how much MB I will need. I will be using data mainly for:
- Checking facebook regularly for about 30 seconds at a time (just my news feed and the random message once in a while)
- Checking email once or twice a day (it's mostly junk so I won't be actually opening the emails to read them, I probably open about 2 out of every 10).
- I won't really be using online apps as I have my ipod touch for that.

The plan I'm looking at offers 150MB so I'm wondering if that will be enough.

Erm 150 might do it but id be safe and go with like 500mb… If you have an android phone you can tell the phone to stop using internet when it reaches its limit… I don't know about apple on this one