This is an open-ended question. You will have to narrow on your own. 500,000 is not really that much. You can't even book a 7-night Cat-8 stay. It requires 510,000.
Things you need to consider:
1. flight and other transit cost. If you are doing island hopping, it will cost you more. Also, transit will take more than one day.
2. Hotel occupancy. Most hotels outside US may not be able to accommodate more than two adults with the standard room. Expensive to upgrade.
3. Related tours etc.