These are great to make sure you're not picking at acne throughout the day. Work best on whiteheads or open wounds (aka popped pimples)--cystic acne tends to be its own beast and it's a waste of these patches to use them on cystic spots unless they're open. (Which they shouldn't be, because that means you probably opened the wound with your fingernails. DO. NOT. PICK. YOUR. SKIN. It's hard, but you WILL leave scars that are gonna take forever to go away.)

So since you're looking to buy 10 packs at once, you're obviously interested in getting the best value for your money:

• know what kind of acne these work on--whiteheads and open wounds. it is futile to hope they are going to draw out acne or clogged pores that don't show much surface activity
• use the sizes accordingly--if your pore/acne is on the small size, USE THE BABY SIZE ONES! there are a lot of them, and you don't really need to play it safe with sizing up. even if a spot is pushing medium, you can still use a small one because the gunk will still come out of the pore and you can save the small amount of medium ones you have left
• buying large medical grade hydrocolloid bandages for night use--i like these patches too much to use them at night. these cosrx ones are pretty transparent and ok to wear out and about if you have bangs covering them or a small spot on the side of your face/under your chin. (I mean, people are gonna notice them if they look at your face long enough, so don't use them for special occasions or anything.) HOWEVER, they're just way too expensive and have way too much packaging for me to feel happy using them at night. each sheet has so much plastic that comes with it, and only 24 patches! (that's a lot of waste that takes forever to decompose for such a small amount of product) SO, i bought a 20 pack of large square hydrocolloid bandages from amazon. they basically do the same thing as these patches, but because they are very noticeable on my pale irish face and you have to cut them yourself to be smaller patches, i only use them at night/at home. my roommates see me walking around with tan squares on my face all the time, but it is way better for the environment and my wallet to alternate between these wonderful cosrx patches and the crude-but-effective duoderm bandages depending on the situation.
• work on improving your skin condition so you don't have to keep buying these (for your wallet and the earth)--I know skincare is a journey, but the better your skin is the less you'll use these. i feel bad having to throw out these patches and fill up landfills, so that motivates me to get better skin and have a routine with less waste. (though note that you can recycle the plastic and paper parts of these). /r/asianbeauty on reddit is a great resource for asian beauty products/ingredients, just try to not get carried away wasting money on products you'll wind up putting in landfills.
• EXTRA TIP:  the expiration date is on the back of these (that's what the 까지 means at the end of 20190919). it is not the manufacturing date like some asian products, so you have a LONG time to use all these patches up (i bought mine november 2016 and am on my second sheet out of 10).