For any others that are looking at this, I used this GF filter to make my buttons one of the buttons included in the kleo theme. You can change the “class” to be any of their buttons.
COPY CODE
add_filter( 'gform_submit_button', 'gform_submit_button', 10, 2 );
function gform_submit_button( $button, $form ) {
$button = sprintf(
'<input type="submit" class="btn btn-primary btn-lg" id="gform_submit_button_%d" value="%s">',
absint( $form['id'] ),
esc_attr( $form['button']['text'] )
);
return $button;
}