I did it the other way around. Built an inexpensive 4x8 layout, 027 track, post war transformer.
Can't say the same for the trains, i have enough to keep the NJHR layout busy. Not complaining/ bragging since most of us have way too many trains. Fortunately I started backing to the hobby in 2016 so after I switched to command control, TMCC and PS2/3 were well tested in the hobby.
I've recently started upgrading older locos with Lionchief and Flyerchief boards. Inexpensive compared to ERR or Stacker installs.
Scenery is where I go cheap. Rigid foam, cardstock printed stuff, dollar store ground covers, and acrylics are the rule.
I do hope to build something of a dream layout one day, Ross, Gargraves, new power, controls, all the bells and whistles. At least I have the trains already.
Bob