In your react native project, in the root there is file "config.js". You should already have set up the connection to your Firebase DB here.
Bellow you will find some configurations for the PayPal and SendGrid email notify.
In order to accept payment in the app, you will need to have merchant paypal account.
Sign up for free SendGrid account. With this in place, you will receive an email when new order is place.
You can use Smooch email, and have thous orders received in Slack
Sign up on AdMob. In the navigation menu you have Apps, click on the Apps and then click on ADD APP. Enter your app name and choose the platform(Android or iOS). And then click on NEXT: Create Ad Unit. Then you have to create banner id or interstitial id. Now go into the project, and open config.js file. Then change the value for showBannerAds and showinterstitialAds to true if you want to show banner or interstitial ads, the default value is false. And then enter your ids that you create.