I use Real flight G2 that I bought used off Ebay.
I specifically went with G2 because the min. computer requirements where more in line with what I have, add to that the fact that it was used and therefore much cheaper.
G2 or G3 come with their own controller made by Futaba and it feel quite alot like my real Futaba radio.
On a very tight budget you can get a cable for your radio and download FMS for free. Not near as good as most other sims it is better than nothing.