How much formula should I give my baby if I am still breastfeeding?

None needed. If your baby is breastfeeding exclusively you do not need to give any formula at all.
Lactation consultant. Insurances usually pay for lactation consultation with a lactation nurse. Often lactation nurses come to your home and teach you many great techniques. Ask your pediatrician which one he/she recommends. It can be invaluable....And covered too. Great combo. Good luck and congrats on the newborn.