Since you can get a complete tablet for so little I think you know you won't beat the price of ready made units.
The question about how folk make software is they learned programming then learned more to create more things. I suggest you learn about the Rasberry Pi since it's a good start to learn about small machines. You can even add a touch screen to that!
Bob
I need to know which parts go in a tablet
Are there any tutorials out there on making a tablet.And which would be the perfect place to buy all the components.
And how do people make softwares like android,I mean which software do they use to make other software,and anyway I won't be doing something complex like android or iOS just a dumb interface

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic