Extension tubes would allow you to focus closer, but of course, you will
have the lens very close to the subject, too.  A tripod, and possibly a
focusing rail will help, considering that you will have your lens stopped
down, and will be using slower shutter speeds.

Close-up diopters are another option - they screw on to the filter threads
on the front of the lens.

Neither of these approaches will give you images that are as sharp around
the edges as a more expensive macro lens.

I've tried all the approaches, and they all have trade-offs. Diopters
let you get closer to the subject than you could without them, but you
will see increased optical defects in your images as a result (edge
softness, chromatic aberrations, etc).

Extension tubes also let you get closer. But they will cost you in
terms of your shutter speed.

The benefits of these approaches are that they are inexpensive.

They did not suffice for me, and I ended up buying a Sigma 150mm Macro
lens. Built like a tank, good optics, great image quality. Plus, you
don't have to be 1/2" away from your subject to get decent
'magnification'.

Tradeoff is that it's not cheap. I paid on the order of $600.

What kind of images do *you* want to make???

Diopter supplementary lenses, reverse rings, using a short lense
(say 50mm) as a diopter by mounting it reversed in front of a
longer lense, extension tubes, bellows, tripods, focusing rails,
ring flash units, "macro" zoom lenses that can do 1:4
magnification, macro prime lenses that can do 1:1 magnification,
flat field lenses, and using enlarging lenses...  are all topics
related to different kinds of photomacrography.

There is a huge difference in what to talk about if the intent
is to take pictures of very small, very flat, or 3 dimensional
items.

With a regular 50mm lense there are a few characteristics that
you'll want to know about, because they restrict what it can do.

Your 50mm lense will almost certainly need something to help it
focus closer, and either a bellows (which will put it into
manual mode only) or extension tubes (which can be either manual
or can provide automatic functions too) will work well.

Supplementary (diopter) lenses that mount like filters do not
have as much effect with shorter focal length lenses, hence only
a very strong diopter would work and of course the stronger the
diopter the more it degrades the sharpness of the lense, hence
that would probably not be as productive.

With extension tubes or a bellows, a short focal length like
50mm will have a very short working distance, but give
significant magnification.  Not Good, if you want pictures of
rattle snakes, for example.  And you'll be so close that most
insects will flee in terror, so that's out too.

It will not have a very flat field either. And it will probably
have a very distinct decline in sharpness if the aperture is
anywhere near either wide open or fully closed.  Basically
you'll only get sharp images at f/8 and maybe f/11 or f/5.6.
That means you cannot get much depth of field for 3 dimensional
objects, and yet it isn't very versatile for flat objects
either.

Some of the limitations do have work arounds though.  For fairly
large objects, such as flowers, a 50mm lense with a short
extension tube will do just fine if you can set the aperture to
f/8 and vary exposure in other ways.  A tripod and focusing rail
might be handy, especially if natural light and long exposure
times are used.  Or two or more flash units can be used
creatively too.

What kind of pictures do you want to take?  Tell us that, and
folks will describe the easiest ways, the cheapest ways, and the
most versatile ways.  All different, and probably all both fun
and productive to some degree.

You might also try using a Canon Auto Bellows. When I had the same camera
and lens you mentioned, I had decent succcess with this setup. The bellows
can be had pretty inexpensively, say $50-100 used. I still have mine, though
I no longer have that camera. You can probably find the bellows on Ebay.