I'm afraid you can't. Even if you buy Videnton Agency without the Standard Version, you will not be able to use Videnton without the Standard version.
Here is why:
1. Videnton Standard Version is the main product which comes as Monthly, Annual or a Special One-Off payment subscription.
2. Videnton Agency is an Upgrade or Up-sell which gives you 5 Additional License Keys for your Videnton software.
3. Since Videnton Agency is not independent, you will need to subscribe for the main product Videnton Standard Monthly, Annual or a Special One-Off payment subscription. Else you can't use Videnton with only Videnton Agency in your account.