I would start putting say $100 a week in. This will give you some BTC. Learn about security and how to transfer BTC etc. This also will provide dollar cost averaging for your investment.
I highly recommend the free Bitcoin video series on CBT Nuggets. The URL is:
http://bitcoin.cbtnuggets.com/I have been into Bitcoins for 18 months now and I just recently discovered that website from another topic on this forum. I am halfway through the 15 videos and they provide a great deal of information what Bitcoin is as well as encryption, multifactor authentication, securing your wallet, acquiring BTC, etc.
I learned quite a bit on my own over the past 18 months, and the videos on that website covered it all, as well as a lot of new stuff. I cannot stress enough how much I recommend it for newbies.