Apart from books, your most important source of information as a musician is recordings. Listen to albums which feature piano or keyboard players. All music is an extension of what has come before it, so you need to be aware of the development of keyboard playing throughout the history of music. Studying Classical music will give you a solid grounding which can be used in any style of music. For more recent styles such as Jazz, Blues and Rock, it is essential to listen to a wide variety of players, some of whom are listed here. There is a lot of crossover between styles which come under the headings of Rock, Jazz, Blues, R&B and Funk. There are many great players in these styles, but the following list is a good start.
Blues: Otis Spann, Memphis Slim, Champion Jack Dupree, Dr John, James Booker, and Professor Longhair.
Soul/Gospel: Mildred Falls (with Mahalia Jackson - "Live at Newport 1958"), Ray Charles, Aretha Franklin, and Richard Tee.
Funk: Herbie Hancock, Art Neville (the Meters and the Neville Brothers), Bernie Worrell of Parliament/Funkadelic, Stevie Wonder, and George Duke.
Rock/Pop: Little Richard, Billy Powell of Lynyrd Skynyrd, Jon Lord (Deep Purple), Keith Emerson (Emerson, Lake and Palmer), Donald Fagen (Steely Dan), Leon Russell, Jackson Browne, Elton John, Billy Joel, Fiona Apple, Bruce Hornsby, Tori Amos, Ben Folds, and Vanessa Carlton.
Jazz: Jelly Roll Morton, Lil Hardin (with Louis Armstrong) Fats Waller, Teddy Wilson, Count Basie, Duke Ellington, Mary Lou Williams, Art Tatum, Thelonious Monk, Bud Powell, Horace Silver, Wynton Kelly, Red Garland, Oscar Peterson, Bill Evans, McCoy Tyner, Herbie Hancock (Jazz as well as Funk), Jimmy Smith (Hammond Organ), Keith Jarrett, Joe Zawinul (with Weather Report), Mike Nock, John Medeski, Jacky Terrason, and Brad Mehldau.