Hi Andy,
welcome aboard!
You will find one thing: thinking, meaning and thoughts on GardenRR are as subjective as can be, and everyone does -in the end- what he likes to do.
Beside that things, there ARE some general rules, which on one might be to a retired person with health problems:
Think about the RR laying DOWN to the ground or making a layout that can be reached while standing comfortable. Man! I am 41 an have a bit of a "bally" silhouette, and i often thought of why that thing has to be so damn deep under my working level.....
Cheapest track isnt the best, the most expensive solutions arent, too.
My track-supplier has a very fine "way of the middle" with nicleplated brass rails. Stainlessis much more expensive and hard to work with, clear brass is going to be oxidated the whole time ( i have RC-Accu-Operation, i dont care about contact problems).
But give yourself a bit of time, looking and searching in this forum.
I found people here making very nice layouts with the cheapest toytrack. An open eye, an open mind and some fine lubricated mechanics in your brain and the ideas will flow!
Greetings
Frank