Getting into macro photography can be relatively inexpensive. There are various options dedicated to macro lenses like reversing rings or extension tubes, but these have their downfalls. Reversal rings leave your rear element exposed and you lose the ability to auto focus; extension tubes provide only a minimal magnification gain with telephoto lenses. There is a third option: macro close-up filters. In the video below, photographer Mike Browne explains what these filters are and how they are used.
Close-up filters are specified in terms of diopters (think reading glasses for your lens), which is a measurement of their magnifying power. Higher numbers yield more magnification at the cost of image quality. Years ago, the quality of close-up filters was poor and most photographers tended to stay away from them, but over the years, they have become better and better.
Unlike extension tubes, close-up filters increase magnification much more when used with longer focal length lenses. For example, a 200mm lens has a native magnification of 0.16x, add a 25mm extension tube and it reaches 0.29x; compare that to 0.96x with a +4 close-up lens. When added to a lens less than 80mm, only a minimal magnification is achieved; at 50mm, the 25mm extension tube is 0.65x and a +4 filter is 0.45x.
Adding this magnifier to the front of your lens does have some pitfalls to consider though. When adding the filter, you lose the ability to focus on distant objects, the additional glass can decrease image quality (thought it may only be minimal), and they decrease the working distance between the lens and your subject. For around $100, you can get a decent set from B&H Photo, now you just need to work on lighting.
(Via The Phoblographer / Images screen captures)