Keep it simple. I recommend dressing yourself first and selecting complimentary (but not matching) outfits for everyone else. Consider both your personal style and the colours of your home.
For newborn sessions I recommend sticking with lights and neutrals. Floral dresses or skirts are also a lovely option for mom. Please avoid very bold colours and large logos or words on clothing as these will be distracting in your images.
If you would like more direction, please let me know, I'm happy to help.