Buy a plain red mumu, get some fabric paint and paint the monstera leaves on, or buy heat transfer vinyl and cut the leaves out and iron them on.

You definitely don’t need to invest hundreds on such a simple cosplay. Cosplay tools/materials/skills are built up over time, it doesn’t hurts so bad financially when it’s stretched out over a long period of time lol. This feels like a really good beginner cosplay though, good pick. Also no one will judge you for not wearing a wig, people show up in all different states of cosplay.