What would be an ideal location for offshore company to trade with India and what are the advantages of it?

Singapore provides a procedurally easy and inexpensive option. Also, the tax rates are kept relatively low, comparing to other Asian countries and that it only taxes on profits made within Singapore, i.e.: if you make a profit in India, it is not subject to Singaporean tax.

With the multitude of Double Tax Agreements (DTAs) and Free Trade Agreements (FTAs) that India has signed up with neighboring Asian countries, offshore companies in this case will enjoy tax benefits, reduced tariffs on thousands of goods. In particular, India maintains a significant Free Trade Agreement with ASEAN bloc, which themselves have certain Free Trade Agreements with China and other Asian countries.