Probably a huge topic. But here's a few pointers I usually use for outside scenes.
A least amount of lights. Probably just one directional light coming from a source (the sun). Decent shadow, with resolution depending on how cloudy the sky is.
Sky - high resolution 360 panoramic image. If I use sky provided by RL, I usually up-convert it to 16k x 8k in Topaz Gigapixel to get crisp sky/clouds.
Rotate it until I get correct position of the sun (if one is depicted in the sky texture). Or sync key directional light with location of the sun in the sky.
GI is must. The Bounce amount and other parameters are set individually per scene. Voxel mode has to be hi-res (set in Project settings).
Either IBL or some amount of bright color Ambient light should be present to enhance the GI and equalize to some degree.
In case of IBL, it should be an outside scene HDRI with some bright spot source for the sun.
IBL should be rotated to match the bright spot with the sun location in the sky and directional light.
HDR effect should be ON with Threshold and Bloom scale set appropriately.
LUT Post Effects (even basic Color Adjust and Color Filter) can be very handy to amplify the overall atmosphere.
As a mandatory, I do place a low intensity shadow-less spot light right in front of the face of each character, enable a tube shape, vary its size to get a good light reflection in the eyes.
Then attach it to the head. Also set very low range and angle so it does not affect other objects nearby.
All of the above should be well balanced and it sometime take a lot of time with going back and force on settings to create a decent outside atmosphere.
It also depends of what you wish to emphasize in the scene. A well composed settings for distant shots might not be appropriate for characters closeup and would require some tweaking.
I usually recommend to bookmark
https://courses.reallusion.com/ where tutorials could be searched per product with specific keywords (like GI, lights ... etc in this particular case).
Just an example of a few different times of a fairly sunny day and different sun angles.