Which is the best field for a person who has a good imagination and creative mind?

You can choose from animation, vfx, animation, gaming, graphic or web designing. Or if you want to pursue a full time design course you can also join a design college like NID, Symbiosis School of Design or DSK.

Creativity has no limits, binding , conditions or parameter. one can be creative in cooking, singing, dancing, drawing, photography , lifestyle or many more . But yes Animation is a pipeline which involves probably the maximum kind of creativity through out its entire pipeline .