No you don't have to start on the ramp, though that is a fun way to start & I wouldn't say never, it was fun for me back in the days when the interface with the operating was greater than now. To qualify a few points I made.
01/ Flight Dispatcher is really a - Flight-Route-Fuel Planner/In-House AIS Briefing person. Interpretation of aircraft performance, terminal & enroute hazards/poss disruptions to flight (NOTAMs/geo-plitical data), meteorological knowledge/interpretation,
The US interpretation of Flight Dispatcher is a historical term created when there was very ATC function back prior to WWII.
02/ Ramp Co-ordinator/Dispatcher is a much more hands on (dare I say Ramp Tramp) application. Very needed ramp co-ordination/awareness/H&E knowledge skills, they are both very different, but of course complimentary.
Where would we be with out the "Honey Cart" man!
For a very first step check
www.cityandguilds.com check aviation.
Good luck which ever way you go.