Okay so I don't know where to buy a binder on the internet. I don't want to buy one that doesn't work well. I am a 34C and am not even sure what size to get. If you could please help it would be great.

I've gotten all mine from Underworks and they have served me very well.

I'm also a fan of underworks.

They have measuring instructions on their website.

For a first binder, Underworks is great. http://ftm.underworks.com/
I'd recommend either the Double Front compression (997) or the Tri-top (983)
For sizing, I believe you measure around your chest under the chesticles and then around the widest part of them, take the average, and that's your measurement. (Does that make sense? I'm not good at descriptions.) Then on the website, they've got inch measurements for the sizes for each model. 
Being an A myself, I can't tell you which would be better for you, but there's plenty of other guys on here that'll have great advice.

under10 is a coupon code that will give you 10% off at underworks.

Thank you the few who replied to my post. 

LesLoveBoat is another good site.  Their binders are more expensive than Underworks but will last.  I've got one from them I've had for over two years and it's not as tight as it used to be, but still works very well.

I have to go with Underworks as well, I've had no troubles so far. It took me a while to find a look that I was happy with but once I got that they're great. Just a heads up if you get the Underworks 997, it does roll up sometimes which can get annoying.

I have the Underworks Tri-top