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 "...
TLDR: Scale for train MOC is a personal preference based on the needs.
There is a lot of personal preferences here. Like, how do you decide if the LEGO track geometry should translate to standard gauge? Why not any other track gauge available in other countries? How do you scale the model if it originally use slightly wider gauge? So there'...
It looks like the best practice is to adjust the proportions to the constraints imposed by the media.
For example, the closest LEGO rendition of a modern high-speed train, the 10233 Horizon Express has cars that are built on a 6x28 chassis piece, which gives a very different width-length ratio than the ICE2 (3.02 m : 26.40 m). And it just works and looks ...
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 ...
If there is a suspicion that the metal surfaces have developed dust and grime or any other insulating layer, a solution would be to give the tracks a Brasso (or other metal polish) wipe and quick rinse and dry with water. Also give the train motor wheels a wipe of the same polish.
Also check this YouTube video https://www.youtube.com/watch?v=RCda7voqyUY