Select the Bar of the barbell and fill it with the gradient as a REFLECTED GRADIENT so that it appears to be a round bar.
Select one of the bells of the barbell and fill it with the gradient as a RADIAL GRADIENT so that it appears to be a sphere. Repeat with the second bell.
Create a gradient for the oval. The gradient should have THREE steps: one color at the beginning to another color in the middle and then back to the first color at the end. You can copy a gradient pen from one end to the other by clicking and dragging with the Option/Alt key down. Select the oval and fill it with the gradient as a ANGLE GRADIENT.
Create a gradient for the polygon. The gradient should have TWO steps AND THEY MUST BE SET TO LESS THAN 90% OPACITY (and more than 0% too). Select the polygon and fill it with the gradient as a DIMOND GRADIENT.
DONE.