You can start investing in commodities by buying commodity futures contracts or ETPs tracking a specific commodity index. This kind of investment is highly volatile and technical, hence not beginner-friendly. The alternative is to invest in physical commodities like gold bullions or silver coins.
Here, prices are pretty stable, but you may incur holding costs such as insurance and storage. Also, you can invest in commodities by buying mutual funds that allow investors to invest in commodity products like oil or energy.