Before you go and purchase any maps, try it out using the free "open cycle map" in the map menu.
I find that the best way to operate with Viewranger is to save GPX route files from walkhighlands to a folder on your pc.
Set up a Viewranger account (free) using your pc, and follow the instructions to import the GPX files to your account.
When you have done this. Open your viewranger app on your mobile and syncro it. This will then transfer those new routes to your mobile.
Before heading out to do the route, make sure to open and view it on your mobile in "open cycle map" mode while still at home with your broadband switched on. Zoom in to the desired scale and your mobile will then download all the map detail.
This saves your mobile trying to download map detail while out on the hills.
All fairly hassle-free and no need to pay for maps.