Terk
Antennas really don't need to be expensive, but you really do want to get it up high and away from other electronics to avoid interference. I have a Terk flat antenna that I laid on the back of my roof so it was invisible from the ground. I think I ended up receiving something over 40 stations pretty well with the antenna and about a dozen when I just used the T-antenna that came with the receiver. I also lost about half the stations when the antenna was in the same room as the receiver.
So, if you can get a piece of COAX (cable) from your receiver location to your attic, you will have done the majority of what you needed to do for excellent FM reception.