In Nigeria, if you want to sell a Play Store gift card worth 30, here are some steps you can consider.

Firstly, you need to find potential buyers. This could be through various channels such as online marketplaces dedicated to gift card transactions, social media platforms where you can post about the available gift card. You might also inform your friends, family, or acquaintances who might be interested in purchasing it.
Secondly, when dealing with the transaction, ensure clear communication. Let the buyer know exactly what they are getting, including the value of the gift card and how it can be redeemed. Provide detailed instructions on how to access the Play Store and use the gift card for purchases.
Finally, be cautious about security. Protect your own information as well as the buyer's. Use secure payment methods if applicable and make sure the exchange is smooth and legitimate to avoid any potential fraud or disputes.