I'm not an expert - in fact, I find landscapes very difficult - but I would process the sky and foreground separately. Either make a selection with the lasso tool or make two copies of the background and then blend. Either way, adjust the levels, contrast and colours for foreground and then do the same for the sky so that each look the best you can make them. Then when they're put together, the result should be better. Hopefully. It's not ideal, but it does at least enable you to make adjustments to the two areas without making a complete mess of the other. If I'm stuck with the lighting, time of day and I haven't got a bunch of filters with me, then I usually expose for the highlights and adjust everything in Photoshop. As I say, I'm not an expert but I hope this helps. James.