For a small transaction such as $50 I would suggest btcQuick. You can purchase bitcoins through a credit card using their service and Google Wallet. The only downside is that there is a 7.5% fee for new members, but that isn't bad in my opinion for a $50 transaction. I've personally used btcQuick twice and have had a great experience working with them!

If you do chose to use btcQuick you will have to verify your identity; which is normal for most exchanges. They will ask for a picture of your ID and credit card (both can have nearly all of the vital information censored out, they mainly want to see your name and the last 4 digits of your credit card number). Verification costs $1.99 and only takes a few minutes, then you're ready to buy bitcoins! They fund a private key or send your bitcoins to an address you verified via signing a message on your bitcoin client. If you don't know how to import a private key or sign a message with your bitcoin client I suggest you practice with a negligible amount of bitcoins which you can obtain through faucets; there's lots of room for human error currently so make sure you understand what you're getting into!

Link to btcQuick if you're interested: https://www.btcquick.com/beta/