To have a good ringtone site is will take a great design and payment/download system as well as making sure you have a marketable logo and name. I would say get a good business plan, find out what royalties need payed and whom to pay them to in India. I would say you need around $10,000 minimum to get this going successfully.
I think you can add some more feature there like file transfer or mobile related product or similar services to monetize it well since the ring tone market seems very competitive.
somebody was offering the service to set one up for you on dp. using a basic template for all of them and a ringtone affiliate but im sure you could get that then just get a custom template done for a few 100. then you have a nice unique store and all the hard bits e.g. ringtone sending and new ringtons is done by the affiliate company you just get a percentage of what you sell
The bulk of your startup money needed will be on advertising I'd say 80%. For example here in the UK, maybe the US. We have jamster ringtones which are just advertised all over the place: the radio, web and TV. And now its a multi-million dollar company.
you need to in someway make your service different from the thousands of other similar services already out there. im not sure how your going to do that, but you need to make yourself stand out from the competition if your going to win in such a saturated market.
You should also advertise on sites like India Forums. They use google adsense, so you can just click the advertise on this site button if they have one.