We sold a rental house this last August. Our real estate agent also recommended hiring a professional stager. After getting a couple of quotes, we decided to do it ourselves. In the living room I placed a couple of club chairs by the fireplace, placed several small tables (one between the club chairs with a lamp, the other two with plants. A picture over the fireplace, a vase on the hearth with tall dried flowers and some candles on the mantle.
In the kitchen, I put a small round table with two small chairs, a tablecloth with flowers. In the bathroom, new fluffy towels, a candle & budvase. I put up sheer curtains in the livingroom, kitchen & bath. Left the other areas alone.
The house sold in 5 days (we had 6 offers).
My advise is this: if the condo is high end,, hire a pro. If not, get some advice from a friend who has good taste, do it yourself and keep it minimal. Don't fill it up; just enhance it a bit. Maybe you can rent or borrow a few pieces of furniture. I used some things I found at thrift stores mixed with some of our own things.