FTM ; need some advice please!

FTM - I have a 2wk old NB, ive been giving her BM but supply keeps changing , one min it's good & one min it's low....i want 2 start giving her formula for when I go back to work (will still be getting BM also) ... but not sure what's the best kind, I've read so many different reviews, so I'm confused, just wanting to hear what worked for you moms & your baby...suggestions