Dish tv / tata sky along with FTA dish

Cable tv in my area I am thinking of installing a dish. I need to know:

1. What are the things I must check while buying a dish?

2. Which is better (and cheaper)b/w dish tv and tata sky?

3. What kind of receiver should I get or FTA chanels (there are cheap ones as well as expensive ones available). What is the difference?

Thanks in advance