It's amazing what you can do with one suit, a skirt, a blouse and a few coloured t-shirts. There are so many combinations. You probably have a few shirts already you can put with a pant suit or skirt. With suiting, when you're just starting out it's important to stick with simple black or maybe a dark navy. It goes with everything and nobody notices if you're wearing the same thing more than once.
Combinations:
pants and jacket with white blouse (if you are going to keep your jacket on you can get a way with a nice looking coloured t-shirt)
pants and blouse/sweater
skirt and jacket with coloured t-shirt
skirt and blouse
pants, jacket, scarf
skirt, jacket, scarf
You really can go far with just a few items. So buying one suit and a skirt with a few inexpensive t-shirts may be another way to go.
Depending on your size going second hand may be extremely hard especially in the plus sizes although it's starting to happen. I found a pair of jeans a few weeks ago for $14.99 Canadian from Value Village. They were brand spanking new and a size 28. I was thrilled. But there was nothing else.
Another option if you're really pressed for money is [url=BellaOnline ALERT: For anti-spam reasons, we restrict the number of URLs allowed in a given post. You have exceeded our maximum number of URLs.