It might help you to pay a visit to one of the site sponsors - sadoun.com or satelliteav.com have both been good to me. You'll find that they sell packages containing everything you need. Depending on who you buy from/what you buy, you may get everything you need, or you may need to buy lnb, dish, receiver, wiring, etc all separately.
To answer your questions further requires more information - i.e. what type of programming you're looking to receive, and where you are located. Dish size varies depending on where you're located and what satellites you want to receive from (fringe areas require larger dishes). There are different types of lnb's and dish sizes depending on whether you are looking to get KU-Band signals or C-Band signals. You may also find a need for different receivers depending on whether you want to receive digital or analog signals.
The most popular items you'll see discussed here, are probably a KU-Band digital setup. This normally consists of the lnbf, a 36" or better dish (can be smaller, but not much), and a digital satellite receiver (and maybe a motor if you're adventurous and want to receive channels from more than one satellite).
Check out the sponsor, and if you have questions, come back with details on what you're looking for. You also might check out lyngsat.com and see what free channels are available on each satellite in your region, so that you know what you'll be looking to receive.