Breast fed or formula opinion

Iv heard mixed things about breast feeding and formula.. If mum doesn't eat right then will baby not get what he/she needs ? I don't eat overly healthy (no judgement) and i was going to try breast feeding but im worried if i do bub's wont get what she needs. I have a friend that has said her baby sleeps better ect once she started formula. I was maybe going to try both ? Opintions would help :) thanks