There is only one dinghy that's truly international. It's been raced in every country I have been that has water... And I believe on lakes in some countries without sea access.
That's the Optimist.
The kids on these are learning faster than other dinghys because there's constant national and international championships. This month alone kids can race from local club level right up to international events on Oman, New Zealand, Brazil, Italy and the Netherlands... And that's just this month. http://www.optiworld.org/calendar.php
Yes the boats are more expensive than you are looking for, but there must be a vibrant second hand market. Once bought the boat expenses should be low.
One kid that races here in St Martin is 10 and he flies off to meets all over the Caribbean. All he takes is his kit bag and own sail, then races the host clubs boats. And wins! His ambition is the Olympics. An Optimist is a starting point.
Have a good think about it and sus out the scene.
. What will it cost?
In North America add around 30% to the prices below.
Around US$500 a year.
It works like this (very like the secondhand automobile market):
US$ 500 - 800 buys a good first boat (pre-owned) - and you can expect to drop $200 when you sell
Trade up every year or so. Reckon on adding around $300 a year to your investment
When you sell your last Optimist you have the price of a good secondhand Laser or 420 - and the path to a lifetime of sailing
If you want to buy new, beginners' boats start around $1,600 + any sales taxes. But see the warning on the technical page
Add a good buoyancy aid/PFD (personal flotation device) and some clothes according to your local weather
Check out fees at your local sailing club
from the website above