The 500 edits required for access to TWL is actually for all of the sites under the Wikimedia banner. If you're having trouble finding things to edit on Wikipedia, you can try their other sites such as Wikisource or Wikibooks.
On Wikisource in particular, it's fairly easy to make useful edits through validating proofread pages or proofreading simple pages (both of which can be easily found in the Monthly Challenge).
On Wikisource in particular, it's fairly easy to make useful edits through validating proofread pages or proofreading simple pages (both of which can be easily found in the Monthly Challenge).