well i personally cannot take prebiotics because my gut has more pathogens than actual beneficial bacteria so i will cause more overgrowth.
but, ive learned its better first to run out pathogens by not feeding them and taking a very strong transient probiotic like vsl3. vsl3 drives out pathogens, helps seal gut lining, and helps organize gut microbes. Behind the vsl3 doses i eat many kefir grains and kefir to repopulate my gut. If i take kefir grains without vsl3 theres typically no "space" avaiable on the gut lining if occupied by pathogens. vsl3 removes these pathogens...
I avoid paying for my vsl3 by asking for prescriptions from my gastroenterologist.