The "c" stands for bytes (I guess originally "characters" but with Unicode and what not, that is not any longer one-to-one with bytes ... the "b" suffix is already used for "blocks" though) but isn't strictly necessary. As you might imagine, the manual page has more information.
Another approach is to use find's own options to exclude certain directories. The syntax is somewhat tricky but if you have GNU find, there is a rich set of conditions you can use to identify particular directories for inclusion or exclusion. A common trick is to select the directories you want to exclude and use -prune on them. So for example