It is not possible to determine the "best" commodity to invest in, as the performance of different commodities can vary significantly depending on a wide range of factors. Some common commodities that are traded on the financial markets include oil, gold, and agricultural products.

Yes, individuals can invest in commodities through e.g. commodity based instruments - such as CFDs and futures contracts or purchasing physical meterials.

It is not possible to determine a "top" commodity, as it depends on a wide range of factors, but top five commodities by global trade volume are: Oil, Natural Gas, Gold, Silver and Copper. However, the popularity of different commodities can vary depending on regional and global economic conditions.