Hello.
I'm not absolutly shore of what I'm saying (
) but dependes on your installation, I downloaded the 3 iso from the fedora site, burbed into cd's and install at my plesure. With my installation I used every 3 cd's but depending on what you want to install you may just need 1 or 2.
Installing from the ftp directly, I don't know, I prefer to have the cd's because if something happens to the systems I can use the cd's to repair it or install all over again.
Hope I helped. Anything let me know