Well, I think we all hit a wall sooner or later so...
I think it is looking quite nice already but as always there is room for improvement. My first suggestion would be to start playing around with the lighting, create a bit of a mood (sunset, midday, early morning) with the shadows that depend on the strength, position and direction of the sun.
If you feel like going for this neutral lighting type of look then I think spending more time on the reflections might be the first thing to go. Now, you don't want to make things reflective like it just rained but just putting a barely visible reflection and breaking it up with glossiness / reflections maps might make it a bit more interesting. The trees especially might look a little more cool with a little more glossy reflections on the leafs - I might be wrong though.
Also, for this types of renders you can play around in your image editing software a lot (PS for example). You can consider adding chromatic abberation, clarity and maybe even some LUTs.
What I think you could also use is a bit of a stronger bump or displacement on those tree trunks. Maybe the composition would be slightly more interesting if the wood area behind the house would be a bit blackened out by the shadows.
For material creation you have so many resources online that its kind of hard to start listing them all - you can check evermotion tutorials, viscorbel's website, grant warwicks lessons, I mean the list just goes on :)
Sorry if this isn't too helpful but I just wanted to sort of start you off. I think checking out some How To tutorials might give you a good idea on how to advance this.
Hope someone else chimes in too :)
Keep it cool dude, great stuff!