+4 on the op shop idea. When I graduated and began teaching (as a single parent), I was totally broke, and I bought all of my work clothes at secondhand places. I still do, as I think paying $30 or more for a shirt to wear to work is just ridiculous. Just recently found a pair of pinstripe work pants for $1 on sale at my local op shop. I go for plain dark or neutral tops and bottoms that ideally don't need ironing, a few pairs of nice black work pants/skirt, and a range of plain tops is all you need. I try to blend in by choosing fairly plain (bland) stuff that fits well and wears nicely (doesn't stretch or get pill). Also, things like staying in shape, ensuring clothes flatter you (not too tight/loose) neat hairstyle, clean nails and simple makeup/accessories really help to blend in.