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