If you don't have gochugaru, you can use some other substitutes.  These substitutes include red pepper flakes, cayenne pepper, and paprika.  However, none of these substitutes will have the same flavor or intensity as gochugaru.  If you're looking for a slightly milder version of kimchi or simply can't find gochugaru, try using red pepper flakes or cayenne pepper. The kimchi will still taste great if you don't have any of these ingredients on hand! It might not be as spicy, but it'll most likely still taste good. Give it a shot either way! Just don't wish it to taste like the real deal.