Before experimenting with antennas, you should make a link-budget calculation first. This would give you information about required power, antenna gain (both sides), margin, transmission speed, etc. If in the end it seem feasible and the EIRP stays below the legal limit (for your country), you could think about how to realize the antennas.
Regarding the link-budget calculation, the free space loss formula (Friis formula) does not apply in most ground-to-ground communication links.