A wardrobe can literally make or break your session.
I highly recommend NOT dressing "matchy-matchy" i.e. everyone in white tops and blue jeans...
Instead, use complementary colors with a color palette in mind. Neutral, earthy, bold tones look great and edit nicely. I would typically recommend avoiding: bright pinks, lavenders/purples & anything neon. Layers - Layering is great, cardigans, jackets (especially if its chilly out), blankets, shackets, hats, overalls, jewelry, etc.
Don't forget to coordinate shoes!