What’s the 1 thing that made a HUGE improvement? Mine is bizarre, but it worked in only 3 weeks

I'm looking for the next "thing" in my skincare routine. My skin is looking a bit dull, large pores, and fine lines. What is just 1 product you swear by? Mine was weird, but it was an omega 3 supplement! In 3 weeks I saw a difference in my skin. Friends were asking me what I did differently. My skin looks healthier and that was the only thing I did differently.