Rs.30 minimum.......what you are referring is cash market ........no?
In commodities, there are only futures which you have to buy in lots unlike cash market shares.
So, minimum brokerage problem may not arise as long as you trade........Copper, Silver, SilverM, Gold, GoldM, Lead, Zinc, Crude. But the problem may arise when you go for small ones like Gold Guinea, Gold Petal etc.
Hence, seek the answers from your RM before trading.