Options Trading would be one approach. You don’t need to actually buy the commodity itself, but instead an option contract that permits you to buy the underlying ( stock, commodity ) at a particular rate by a particular date.

If the price were to rise in the future, the value of the contract would be much higher than what you bought it at, and someone interested in further trading in the options contract or even buying the actual underlying world more pay the market value of that options contract to you.

I just checked: the current price of a single options contract of crude for 18 Sept at buying price (CALL) of USD 10, is 0.3. So buying a 100 (the minimum), would cost about USD 30. Now, ID between now and September the price of crude were to shoot up, then the market price of this option would likely rise.

Unlike stock, though, Options expire. But unlike stock, you get to buy the rights to buy or sell at a particular price and thus the capital needed is far lesser.