Online Gambling is not fully legal in India except lottery in a few states. But many operators accept Indian traffic. The Indian market has a strong affinity to gamble on poker, lotteries and cricket. Some table games are also popular and online bingo is picking up with some TV shows. Bingo is not common to people in India as much as in UK, but we use to play housie/ tombola when we were kids and it is very much a family game.
As far as language goes, English is the preferred language. The target market can speak and write in English and are open to online transactions, one of the most important factors when you look at India as a market.