Cantonese is incredibly difficult, I applaud you. I mess up my 4 tones all of the time and thats basic mandarin. chinese grammar would be a good one, not just flashcard style learning if that would be possible. what do you think?
Actually, one can get by in Cantonese without paying too much attention to tones providing you take a run at it and don't use just single words. Context is what aids understanding. But I really would like the memrise team to add audio to all the language courses (gardens?).