Best way to invest in gold?

Would any of you have a tried and tested way to invest in gold through an app/website that you are happy with? I have a mix of equity, debt and traditional (FD for emergency) and looking at adding gold to my portfolio. Idea is to move a certain amount every month. I would like to track the value and sell easily if needed. Temptation to buy jewellery is high but I'm resisting as it's not a good investment idea but am also exploring buying coins from say, Tanishq as they have 24 karat gold so resale won't be an issue and can be converted to jewellery for when my daughter is older.

Any advice would be greatly appreciated!