The problem with commodities is there are many types: oil, aluminum, corn... So some have developed different indexes to track them . First, we have the Goldman Sachs Commodity Index (GSCI), very biased towards oil (energy weights 72% of the total index). There is an ETF related to this index, but with a better sector distribution: GSC (link here) -energy 18%. Second, we can use the Rogers International Commodity Index, linked to an ETF with ticker RJI (link here) -energy 40%.
Of course there should be some correlation between commodity indexes and gold, initially because gold is part of the index basket, but also because gold is also a commodity. However, gold sometimes works as money, basically when investors don't trust Central Banks. And this is what we are seeing lately: gold is breaking the correlation and is starting to move on its own, as we can see in the following charts (red line gold):
Central Banks have a very poor record forecasting inflation and economic growth, however they are more powerful than ever. It might make sense to hedge the risk of Central Bank's miss performing again and buy some gold.