In a nutshell, create a drip campaign that triggers when a contact is pulled into a custom list that collects members who match a specific deal stage.

In ActiveDEMAND:

Step 1

Create a single value picklist custom field on a contact that will hold a deal stage value. 

Administration->Account Settings->Custom Fields [Add Custom Field Type] 

Be sure to list the deal names exactly as you see them in Pipedrive. If you have more than one pipeline, you may have to add the pipeline name before the deal stage, one per line.

Step 2:

If you have not done so, set up a new import scheduler.

Contacts->CRM Contact Updates [New]

In your import scheduler, map deal stage name to your custom field.

Step 3:

Set up a custom dynamic audience (list) that collects members based on your custom field (deal stage). (Contacts->Contact Lists)

Step 4:

Create a new drip campaign (Automation->Campaigns->Drip Campaign

Select the 'Added To List' option

Step 5:

Select your starting step, choose your list