Making the terrain plates is a bit tedious and messy so I suggest you make them in big batches and store the ones you don't use for later.
Speaking of tools, the two most used "power tools" for terrain making in my shop are my Proxxon hot wire cutter and my dremel. I haven't really discussed the dremel and its uses on the blog so I'll do a post about it in the next few weeks.
Here in the states you can get the tile grout pre-colored. I used the earth-tone color which is great for terrain work. There's also a sandstone color which is perfect for desert terrain.
My inspiration for this project is a series of jungle terrain videos that were made by Mel the "Terrain Tutor". I watched a lot of wood working and terrain making videos during my recovery and came to really enjoy Mel's work. So much so I actually became a Patreon sponsor. Take a look at his stuff - it's well worth your time.