Dear Afshad,
What I understood is, company has two global categories (say A, B). Requirement is to create new valuation types (say Y,Z) and assign it to the new Plant (XXX).
Create valuation types and assign it to valuation category (either A or B) as per your business.
Activate these valuation types to only to your new plant.
Then while creating material master for this new plant, only these two valuation types will be shown and these will not be appear for other plants.