First off, fill your Area with grass.

You can start by grass tuffs (i do it like this)
But it really wont make any difference between starting with bushes or grass tuffs.
Remember to use a big round brush, will make things easier. Later you use an 1sqm brush for small detailing.

Then, use it with intensities, means, some parts have more tuffs, others have less and others dont have.
Remember, putted too much? No problem, just erase it.

Then start the bushes, they are your nature shape. So you will have to define the Nature concentration (the places where the nature is growing most)

Then place the bushes.
Again, putted too much? Erase it.

Now the trees, just put them ramdomly and try to put most of them next to the bushes. Of course, there is always exceptions.

Now using dirt grounds, with the autoborder ON just trace a line where you want it, and make it just a LITTLE bit proporcional sided.

I did a simple road. Nicely ramdom and stuff

2 signs for lost travellers… and some stones here and there.
But, wait Farage, wtf is this? Too much stones man!

No problem lolz. Erase
And as a final detailing, i just organize the nature a little bit here and there… and there you go, the place is ready ^^