Question! From EBF to supp with formula...

I have never been one of those women who get 5-8 oz each pumping session, most I ever got was 3! Anyway, I was determined to EBF and I did for about 12 weeks but then returned to work and am now pumping and producing less. I've done the fenugreek, smoothies, etc but it's not increasing and baby is demanding more. So I started supplementing with gerber good start supplement formula. Now I'm kind of clueless as to how much to give at each session and how frequent to feed her. I am so far trying half breastmilk half formula and she takes between 3-5 oz depending on how long it's been and if I breastfed her right before. Can someone who is also doing this tell me their schedule???