What can you do with 150mg data per month for iPhone 4s and how long will it last?

I'm planning on getting an iPhone 4s towards the end of next month and my current service provider has a plan that includes 150mg of data every month for $50. I'm just curious as to what exactly you can do with that amount of data. I know the basics of what uses up data; Facebook, Twitter, Snapchat, internet browsing. But games (Ice Cream Jump, Temple Run, etc.) don't use data, right? I will be connected to Wi-Fi more often than not. Also, I don't plan on being on the internet the whole time I'm out anywhere. I would basically just use it to browse Facebook, Twitter and maybe to use Snapchat.

So, what can you do with 150mg data per month with iPhone 4s and how long will it last? Is it worth it? Does it tell you how much data you've used, when you've approached your limit and/or when you've used it all?

Added (1). Thanks everyone for rudely pointing out that I meant MB.

MB***

Added (2). My boyfriend has a Samsung Galaxy and he only gets 50MB of data every month and he's been managing with it just fine. Can someone please tell me if the iPhone tells you when you've almost used up all your data? Also, does Siri use data?

Mg stands for Milligrams.--

Do you mean Mega Bytes? 150 Mb is very little, i'd use that up in less than a day.

Its enough for you to check emails and browse the net. But if you watch youtube videos, or download files, you'll burn through that data in one day. Its not a lot at all, I recommend choosing a plan that gives you at least 1GB (1024 megabytes) of data per month

Lol it is kind of funny when you keep saying MG

Its MB and in 150MB you can just do very little amount of web surfing. Basically this package is for emails, whatsapp etc. Where you can't download or upload much stuff but you can keep connected to internet!