supplementing?

chloe🌸 • Mother of 1 little boy born on 12/13/2016 & step mother to an awesome 7 y/o.
I've been thinking about supplementing with formula. As of right now I'm breastfeeding, along with pumping. I know my milk will diminish if I don't pump for every missed breastfeed. But I'm wondering, what kind of formula do I use? I know absolutely nothing about it..and there's so many different kinds!! And if you supplement, how is it going for you? Thanks ladies.😊