You can specify a pre-set initial quantity by manually editing the Add to Cart button URL (add &quantity=10 to the end of the URL); however, this will not prevent the buyer from manually editing the quantity to some lower amount in the cart screen directly, so you will need to be clear to buyers on your site that your minimum order is for 10 kits. As another approach, you could sell your product as 10-kit packs, so the Quantity would indicate how many sets of 10 they want to order.
For the volume discounts you want to offer, you would go into Seller Admin > Edit Cart Discounts and create several automatic (no code required) discounts for each quantity "level" where you will offer a discount. You can specify your discount-level thresholds either by order-total dollar amount, or by quantity of items in the cart (which may be easier to maintain if you raise prices later).
E.g. Set your first discount level like this:
Discount name = 26-50 Kits
Discount Code = blank (so it would apply automatically)
Discount = % 13 or 14 (one will be slightly less than $25 each, the other slightly more -- see below)
Minimum order amount = 0.00
Minimum items in cart = 26
Maximum use count = 0 (which means unlimited uses)
Expires on = leave as-is, or change to expire on some other particular date
Then SUBMIT to save your discount settings, and start configuring your next Discount levels -- one named "51-150 Kits" for 35% off a minimum of 51 items in cart, then your final Discount level named "151+ Kits" for 42% off a minimum of 151 items.
Since per-item-price dollar-amount discounts are not an option, and can only do whole-number percentages that cannot meet your price points exactly, you may wish to promote your discount as a "buy X kits get Y% off" deal, rather than "buy X kits for $Y each".
