If gravitational field is not real, then am I gaining energy?

In the frame of reference of a freely falling body, you are gaining speed or energy(assuming you are standing on the ground), because the normal force is accelerating you and doing work on you(in that frame there will be no gravitational force). If that normal force was not there then you to would be in free fall.

Now in your own frame, you are not accelerating, despite there is an upward normal force because there is some force that is similar to a pseudo force acting on you. That is gravity.

Additional Note: One important thing is that Gravitational effects are not exactly equal to the effects caused due to acceleration inside an accelerating frame in space. The equivalence principle works only locally. In a variable gravitational field, we can do nonlocal experiments and find whether it is due to gravity or not. In this example since you are small compared to the radius of the earth, we can assume uniform gravity.