I'm afraid you can't. Even if you buy Promoyze Agency without the Standard Version, you will not be able to use Promoyze without the Standard version.
Here is why:
1. Promoyze Standard Version is the main product which comes as a Personal License or a Commercial License.
2. Promoyze Agency is an Upgrade or Up-sell which gives you 5 Additional License Keys for your Promoyze software and allows you to integrate your Pixabay API to get Royalty Free Images.
3. Since Promoyze Agency is not independent, you will need to buy the main product Promoyze Personal License or Promoyze Commercial License. Else you can't use Promoyze with only Promoyze Agency in your account.