How long before you know a product is right for your skin? [product question]

Beauty Tips For Body Care
I have recently ordered two new products, and I know you are not supposed to use them at the same time to see if they break you out or not. Just wondering how long I should wait until I can introduce the second product into my routine?For example, do I use the first product for 5 days and if I have no new breakouts introduce the other one?
Girls Blog 2015
Submitted by BestCream