Best way to invest in Gold for long term. Plz guide me.

I am confused between Gold Saving Mutual Funds, Gold ETF, NSEL's e series gold . I want to invest through SIP in Gold for 7-8 years. Kindly tell me which one is the most cost efficient and best option available out of above. In case of mutual fund then tell me which is the best mutual fund for gold. Does buying ETF cost additional charge in form of brokerage in compare to others