Local guide is a volunteering program, you won’t get anything for contributing on Google maps but Google will recognize you as a Local Guide for your contribution. Anyway, you will get points for your every contribution on Google Maps and you can raise up your local guides levels.
However, Google Local Guides perks depends on quality contribution on Google Maps; Google sends some perks to Local Guides for high-quality contributions. Moreover, to receive perks, you must be subscribed to emails about them and contribute regularly on Maps. Please be sure that your email preferences have perk emails enabled by visiting your Local Guides settings .
For more details please read the Question about a Local Guides reward email? Read this first.
You may also read the very recent update post about Perks by a Google Moderator: How to stay connected for special event invites and early access