Everybody has given you great advice, so I just wanted to add - I'm a believer in ironing. I hate ironing, but it can up a semi-casual top to work-worthy. Ironing and Magic Sizing is your friend and can make you stand out looking crisp when everyone else looks like they pulled a shirt out of the dryer and stuck it over their head.
I buy lots of tees when they go on sale at Land's End, and pair them with LE cardigans. They have great sales! In fact, I buy a lot of my wardrobe from LE because they carry petites and the clothes are classic and hold up. For work my goal is to be covered and presentable, and if my clothes are a tad boring, so be it - I'm not!