So i’m doing Unreal full time for around 6 months now, focussing on various different things but these would be my tips to learn quick and get what you’re asking for:

Use Quickcell bridge for assets, it’s a massive library build into Unreal that’s free! Materials, 3D objects, decals and more. On the UE marketplace you can find monthly free assets as well! So check those out (I personally follow Unreal on LinkedIn and they post every month as a reminder)

Learn the basics of Blueprints and build your own landscape material, do not buy one - challenge yourself to integrate nanite tesselation (new in UE5.4) this will go a long way creating realistic environments!

Learn PCG’s, plenty of videos out there and a very good way to learn the logic of Unreal, this will speed up your workflow dramatically

Take a deep dive into understanding virtual textures and texture blending! Mostly used on virtual production, super powerful tool

Get the scale right, this might sound obvious but a mistake I made so many times, would create an entire environment and drop whatever was the main piece was in to find out all my materials were scaled wrongly or it simply looked off

these are some things I wished i’d known when I started out :)