Shorter focal lengths work best, in the sense of closer focus and more magnification with extension, so the 30mm should be interesting to try. The 50mm should be fine too.
I'd suggest a cheap set off ebay, with electrical contacts so you retain aperture control.
As you add more extension to the lens, the closer you focus. Like macro, the depth of field will drop rapidly so you'll have to juggle small apertures, enough light, hitting diffraction softening and showing up all the dust on your sensor! Also the lens will behave differently as you are pushing it outside its design limits. Stopping down does help. For example, on the 50mm f/1.8 you get field curvature and a glow if used wide open, which cleans up nicely or is masked when stopped down to f/5.6 or more.
If subjects allow, I find using a tripod optionally with macro rails to be a nice way to work around the chronic light fall off. Alternatively if you do hand hold, get your flash skills on standby.
See also here
for an example of what extension tubes do with the 50mm f/1.8.