Diet: Google studies/papers/articles from dieticians/scientists. Nutritionists is not a protected label anybody can call themselves that
Exercise: also Google/YouTube. Look for licensed physical therapists, trainers, scientists
Skincare: I go on r/asianbeauty, r/skincareaddiction is okay but a lot of stuff like moisturizers, sunscreens, toners, east Asia has the best products but SCA is too white to know that
Fashion: Real life inspo, go to music shows, shopping centers, skate parks, anywhere with fashionable people. I also like TikTok for this. Instagram is a bit too fake