Neutral colored cardigan (white, black, grey, beige)
the LBD
white/black lace cami
confidence (corny, but seriously!)

casual tank or tee (depends on preference)
dressy top
dark jeans (preferably black, so you can dress down or dress up)
skirt (casual/flowy/tiered/pencil,etc)
cardigan/outerwear depending on the season.
LCD (little colored dress -- black looks nice on everyone, but wear a colored dress to stand out even more! Red is the color of confidence!)

If shoes could be considered pieces of clothing then you need
shoes (dressy, sporty, casual -- aka pumps/heels/boots, sneakers, flats/sandals)
& no, this does NOT mean you need 3 pairs of shoes, you actually need more.
because you need the same exact shoe in different colors. yeep. girltalk!

Jeans that fit well in different washes for casual wear.

Jeans that can be dressed up, usually in a darker wash. 

Black pants that fit well and are basic.

A nice Blazer.

Layering ts and tanks with no embelishments and in a variety of color.

Figure flattering skirts in neutral colors. 

Cardigans in a variety of colors.(can go over anything)

a trench coat.(can be worn all year round)

an LBD - conservative.(black allows for accessorizing in complimenting shades of almost any color)

classic pumps in neutral colors. 

neutral colored flats.

brown or black boots.(with pants in winter or dresses and shorts in summer)

a quality handbag.

pear earrings and necklance. 

a good belt for pants and skinny and thick belts for over shirts. 

Day dress

sunglasses, good quality bag, plain white t-shirt, cami's, winter jacket, summer jacket, fancy dress and casual dress.. there's more than that in my closet though :)