I want to make some realistic renderings with GI but now i wonder how to set up for proper lightning. (yes i have tried)

I want to use the directional light for GI, but as i do not have 100% enclosing (top/sides(bottom) and reflecting surrondings, i only get GI light on parts of the model, which makes this light too bright in contrast to the direct light from the directional light.

So it looks that i need more direct light, but i thought the best would be to ligth the whole model up with GI for a realistic result.

If I make a sphere around my model the light from the directional light wont get through the sphere.

Please give me some advice.