Just go for it. If you want toys that look accurate to the show/books and look great displayed, go for ERTL.
They look great on a shelf, and if still in the package, can be hung on the wall with a push pin.
If you actually wanna play with the fuggers and don't care about accuracy, I recommend Wooden Railway as they are cheap, plentiful, and have lots of neat interactive shit to mess around with. Plus making layouts on the floor is fun.
DO NOT GET INTO THE ELECTRIC TRAINS! THAT SHIT IS EXPENSIVE!