Smoothie,
When I started out a few months ago, I bought a hydrometer ($10-15). I couldn't get an accurate enough reading with it so I looked into a refractometer. I couldn't justify the cost of the digital, (over twice the price) so I bought the analog/manual one. It works great and I am happy with my decision to not get the digital one. I use it every few days and every water change. Get a refractometer, you will be pleased.
Kelly