i am intermidiate in english language.i need preparation for GMAT.should i do shelf practice / take coaching?

i need to admit in MBA.so i need a preparation for GMAT.but i am confussed.as ,in home i don’t know how to start and from where to start for GMAT?i have bought some books on kaplan,princeton and official GMAT.but don’t know which one of these books will be more easy to learn for me.