Hello yghtim,
In short, the way to get your lighting correct is to use a combination of the three features you mentioned. Direct lighting, Sky lighting, and Post-Processing. My first suggestion would be to disable the ‘Auto-Exposure’ feature within the post processing settings. Then decide whether you want to sacrifice a little performance for quality by moving to a ‘Movable’ Directional Light and a ‘Movable’ Skylight. These mobility types provide the highest visual quality and mutability.
Post processing is your friend, but if used too extremely, can be your downfall. It is all a balancing act between lighting and post processing. Looking at your image, you will want to add some height changes in your landscape to give it a more organic feel as well.
Your best option would be to take a look at our documentation on Lighting the Environment to get a better understanding and knowledge of how lighting can be optimized to get the desired look and feel for your scene.
Let me know if you have further questions.
Cheers,