Here's a 'simple' way to get the YouTube subscriber number from Google's Youtube API v3:
- Go to https://console.developers.google.com/apis/library
- Log in with your Google account.
- Next to the logo click on 'Project' and 'Create project'. Name it whatever you want and click on 'Create'.
- Wait until the project is created, the page will switch to it by itself, it will take a couple of seconds up to a minute. Once it's done it will be selected next to the logo.
- Once it's created and selected, click on 'Credentials' from the menu on the left.
- Click on 'Create Credentials' and choose 'API Key'. You can restrict it to specific IPs, or types of requests (website, android, ios etc.) if you want, it's safer that way.