London travel help ????

Hi, i bought a Oyster card with �5 credit. I need to travel 5 days a week with train from morning to evening from zone 2 to zone 6 from thornton heath to clapham and from clapham to chessington via train so how much does it cost for 1 day i don't know nothing about it it would be great if you can help me with it as im new to travel in London. Thank you very much.