What transformers do you use and why?

theres one resale shop in my area and i been needing a G scale engine but man the problem is taking the chance because its a shay style engine for like maybe 200 bucks but the downfall it comes in box untested you dont know if it works or not and last time when i bought the circus train the steamer didnt work. and the other i got that did work was a battery powered one so yeah its iffy