I really want to like Korean skincare but at least among the products I've tried, I find that once the novelty effect is gone they're not actually that effective for me. The ones I've tried are:
SKIN1004 Centella Soothing Cream - loved the texture the first few times I used it, but I think it was more the novelty effect. Found it too light and maybe even a bit drying even though I have fairly normal/balanced skin
Laneige Water Bank Sleeping Mask - same, really lovely to apply but simply didn't deliver the moisture I needed...
Biodance collagen mask - again, great novelty effect with the mask melting into your face and I did look glowy right after taking it off, but I was back to my old self within an hour or two
Dr. Jart masks - meh
Cosrx snail mucin cream - really clogged me up and broke me out, I know a lot of people love it but made me look like a hormonal teenager
Anua azelaic acid serum - I didn't dislike it, but didn't see any improvement either despite being consistent and going through two bottles
One I did love was the Laneige lip mask - I will definitely be re-buying that!
I'll probably try a few more because I'm a sucker for marketing, but I've found French pharmacy more reliable and effective for my skin, despite being a bit boring by comparison!
That's just me though and plenty of people have great results, so don't let it put you off if you want to have fun with it - just sharing my experience.
One thing I've found super effective for skin tightening are peptide products, you might want to look into those!