I'm assuming that a lot of your tops could probably be ok if worn under a blazer or cardigan to work (I know I was amazed by how many of mine where when I worked at a courthouse last summer)
to start I'd get:
2 pencil skirts- black and grey (or maybe cream/taupe depending on the colors you like) (lets say this will costs $100)
3-4- cardigans (can probably be done for $150)
a few button downs (lets say $200)
and two pairs of pants- black and one other color ($200)
and 1 blazer ($150??)QUOTE]
^^^That's a good place to start but I think straight skirts (rather than pencil) are more appropriate and more comfortable for work IMO.
Rather than 3-4 cardigans, I only think you need 1 cardigan in a neutral colour, one flattering fine wool sweater. If it gets really cold you can wear them as a twin set.
At least one shirt is a must and a couple of good quality tees.
Try consignment shops for a good quality jackets as good tailoring is usually very expensive. Just because you have to budget doesn't mean you have to compromise on quality
Congratulations on your new job and I wish you the very best of luck