It's possible to visit giant buddha, stanley market and the peak in one day, but you will spend too much time on the transportation, since giant buddha is located on the lantau island, while stanley market and the peak are in Hong Kong island.
From tsim sha tsui to giant buddha, you can take Hk metro tsuen wan line to lai king, transfer to tung chung line to tung chung, walk out of the station from Exit B to take bus no. 23, vice versa. After going back to Tsim Sha Tsui, take tsuen wan line to central, transfer to bus no. 15. Then take bus no. 15 back to central to take bus no.6,6x,6A,66,260 to stanley market.