Hi,
Welcome to the world of railway modelling.
In the first instance I would recommend that you have a look at a few model railway magazines first for some inspiration, Railway Modeller, Hornby Magazine, Model Rail and British Railway Modelling (BRM) are all quite good. Also some track plan books may be of use ( I have some if you are interested).
Also you have come to the right place here, as there are a lot of modellers who can help and advice you.