If any combination of all your products would qualify towards the volume discount, you can do that with a series of discounts on the Cart Item Total with a Minimum Item Quantity -- e.g., in your example, you'd take a flat 10.00 (or 16.7%) off the Cart Item Total when Min. Item Qty. = 2, and a flat 30.00 (or 33.3%) off the Cart Item Total when Min. Item Qty. = 3. Leave the Discount Code field blank to make these automatic discounts that kick in when each qty. threshold is reached.
However, if only some items would qualify towards the discount and not others, the only way it could work is if all of the qualifying items are set up as Variations/Variants of a single product. This allows you to set up a product with menu(s) for buyers to select product options such as size, color, style, etc. -- which can affect the item price, shipping weight, or inventory in stock if you set them up as Variants:
In that scenario, you'd set up the series of discounts on the Item Unit Price of that product. Note that the Flat Amount option in this case marks down the original per-unit price of the item by that amount, so that gets multiplied by the qty. ordered of that product, and the Min. Item Qty. threshold here only counts the qty. of that specific item. You may prefer to set this up as a % Off if your product Variants affect the item price.
