For a detailed list of what others have found out through experimentation and looking at the japanese wiki you should take a look at this: http://harem-battle.club/peropero-se...itos-nest.html

I try to put in R-gachas for my cards but so far it hasn't worked. I got my SR the second time I tried with a Pero pudding and 2 R-gachas. The rewards you get are based on how much time you have to wait, which is based on how much the items you gave her. Different people got lucky with different things but I recommend trying the cheapest methods first, however if you have a lot to spare and feel like changing it up then look at the link to see what you may get.