Choosing the right formula

So based off where I live WIC uses Enfamil, I hate the thought of putting lo through trial and error with formula. I am breastfeeding and did speak to one of the wic consultants and she recommended supplementing with formula but didn't say which type. Based off what I read a lot of moms used Supplementing, Gentelease, Reguline and Enspire. How do I know what's right? I'm still given checks for Infant formula.'