You generally need just one floppy image, the floppies/boot.flp file, which you image-copy onto a 1.44MB floppy and then boot from in order to download the rest (and the installation will manage your TCP/IP connection, deal with tapes, CDROMs, floppies, DOS partitions, whatever's necessary to get the rest of the bits installed).
If you need to download the distributions yourself (for a DOS filesystem install, for instance), below are some recommendations for distributions to grab:
Full instructions on this procedure and a little bit more about installation issues in general can be found in the Handbook entry on installing FreeBSD.