How much formula

Sofi

I started my 2 and half month baby few days ago on Similac advance , not sure if this is a good choice. I breast feed and started doing this in case I run out or when I go back to work so by then he is use to it. For breastfeeding moms, how do you manage to find a routine between the two. So far I use it only on car rides or out of the house.