That'd probably be stuff like skirt or pants suits, blouses, blazers, dress pants, sheath dresses, but in neutral colours [grey, brown, black, off-white], not provocative [no skirts above the knee, midriff covered, dresses can't be backless, nothing low-cut], and not overly embellished [no sparkles, spangles, loud prints, bright colours, huge jewelry]
Minimal or neutral makeup is good, hair is best in chignon, low ponytail, clip, or down and neat.
Jewelry should be minimal; one or two rings, small hoop earrings or posts, one necklace.