While there has only been one DLC released, Frozen Wilds, The complete edition should also have the added items from the Deluxe Edition as well. But I dont think they are a big deal.
The Complete Edition is currently on Pre-order for $49.99....But you can buy the regular version for $19.99 and the Frozen Wilds DLC for $20 and it would still be cheaper then the complete version.
https://www.amazon.com/Horizon-Zero-Dawn-Complete-PlayStation-4/dp/B076BJ723V
Includes Frozen Wilds and Digital Deluxe contents.
Charity links:
I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.