Hi, i’m interested in creating a big landscape for my camera to roam around in and i was looking on youtube and i found this really cool video
Can anyone share some advice for me on where to start, in creating something this cool? 
From the looks of it, it’s simply a subdivided plane with the verticies moved by proportional editing and a simple material, then the person added a basic lighting scheme and an image texture for the sky.
If you end up using the internal renderer, do note you would have to animate a path for the camera and then render out all the frames. It will not be real-time and you wouldn’t be able to horse around spinning the camera here and there at your whim, for that you would need to use the BGE which, if done right, can produce a similar looking scene where you can roam around in real-time going wherever you want according to keyboard input.
It looks like what can be done with “ANT Landscape” script in Blender. It is included in addons by default, just need to activate it in preferences.