Everyone's skin is different. I've noticed that some Korean moisturising sheet masks have done wonders to other people's skin, but because it was too moisturising, it clogged up my skin. Same with mud masks- I avoid them at all costs since they overly strip my skin of its natural oils!
I avoid anything with fragrance (synthetic and natural cause natural fragrance is just as bad) since my skin is sensitive, and sometimes products that aggravate my skin triggers acne breakouts.
Basically, it's all down to experimenting on your own skin. Figure out what your skin type is, do research and create a mental list of ingredients you should avoid for better, clear skin!
I highly recommend watching Dr Dray (licensed dermatologist) and Skincare by Hyram on Youtube. They give invaluable advice regarding what to use and what to avoid for each skin type. They have information on almost every subject about skincare.
I also recommend skincarisma.com! This tool saved my life! It analyzes the ingredients of your products (cosmetic or skincare) and gives you a list of which ingredient does what, and whether its good for whichever skin types you have (i.e. dry, combination, acne prone). This analyser tool saved me the trouble of trying new products out only to find they don't work for my skin and waste huge amounts of money.