extension tubes (back) and diopters (front) can accomplish the same task of being able to focus closer to subjects however by doing so you will lose focus to infinity. Also if you are unfamaliar with working close, the depth of field is extremely shallow the closer you get to the lens. The diopter is the cheapest solution and allows you to play with minimal investment. Also note that the longer the focal length, the longer the extension tube would need to be...take a look at this article...

http://www.shutterfreaks.com/Tips/ExtensionTube.htm

A true macro lens is the best solution since it doesn't cripple the lens in the process.

I bought a +5 diopter for my 50mm prime for $10 to "play" with before buying a true macro lens (Tamron 90/2.8 macro).

I know nothing of them so can not be of direct help but thought I should mention there was some discussion of them here also

http://www.alphamountworld.com/forums/sony-digital-slr-talk/extension-tu...

"1. Do the extension tubes decrease the aperture?"
Yes. Since tubes move the lens farther away from the focal plane, its effective aperture will decrease.

"2. Does the image quality lower when using a extension tube?"
Standard non-macro lenses are not optimized for close focusing, so there could theoretically be some problems with field curvature and focusing aberrations. But for most situations, these things don't pose a big problem.

"3. Should I get the Kenko extension tube set or a macro lens?"
They're both worthwhile, so it's not necessarily an either/or proposition. Depending on the magnification you require, you can also consider front-mounted close-up lenses. I use all three of the above methods depending on the circumstances. Historically, people used to start out in close-up work with auxiliary lenses, then move to tubes, then a dedicated macro lens. But you can start with any of them depending on your interest and your budget.

This article provides a good summary of the various ways to get in close:

http://en.wikipedia.org/wiki/macro_photography

Would I be better off getting the extension tube set now or save up for a macro lens?
I would be using the lens for macro and potraits

"I would be using the lens for macro and potraits."

Your 50mm lens can already handle portraits, so buying tubes won't help there. If your budget allows it, consider a macro lens in the 90mm to 100mm range instead. These can also double as portrait lenses and they provide a different - and often better - perspective than your 50mm can. Some third-party lenses in this range are inexpensive and reportedly very good, like this one (be sure to read the user reviews):

http://www.dyxum.com/lenses/detail.asp?IDLens=236