People often ask me what sort of model trains layout they should choose. This is a bit like asking someone else to name your baby and it should be your own decision.
Take a look at as many different model trains layouts as you can and get a feel for what aspects you like. You may like the multi level scenery of a mountain railroad or you may prefer the busy activity of the marshalling yard, Nobody can tell you what is best because the best is what you like.
I have tried to include a little bit of everything in my train layout but that always results in a compromise so it may not suit you so well.