To dream of seeing someone else wearing a g-string (or gee string) represents something in your life that is noticeably or dramatically revealing itself to you. Opportunities, new situations, or insights are presenting themselves in manner that is difficult to ignore.
To dream of wearing a g-string represents your own powerful interest in revealing yourself, opening up, or taking part in something. You may highly motivated to make intentions known.
Alternatively, it may also reflect sexual interest.