There's already a good answer for where to get the track pieces, so I'll tackle the reset.
Also, since I don't have any brick, what set of random blocks, for the support structure, is better?
If you are relatively new to building with LEGO, building a custom roller coaster design may be a really difficult first challenge.
There aren't any official LEGO ...
You can buy tracks directly from LEGO. You go to LEGO service web page and follow steps below:
Click on BRICKS & PIECES just below the banner
Then BUY BRICKS
Provide your age and location (please be aware the list of countries where LEGO is shipping to is limited)
On the left side you have an option to chose parts from particular set. In this case use "...
Depending on what you are planning to do, there are several options. @Rin Rio-Oki showed solutions for when you are planning to build a fence-like structure, but if this is supposed to be a solid wall, here are three options:
The option furthest back is where you use a 1x1 brick with side stud and a tile in the corner. You could alternatively replace one of ...
Here's an attempt at what I think you might mean, an offset wall that turns a corner while somewhat maintaining it's aesthetically balanced negative space between the bricks.
I'll upload the build file, if this is what you're looking for.
(Of, course we're focusing on the wall not Picasso's Junk Lighthouse behind it.)