Age when Considering gauge
First thing that should be considered is age. If small children will be playing with the model trains, you should consider a large scale such as G Scale. G Scale locomotives, rolling stock, and support equipment are usually sturdier and easier to assemble than smaller scales. Features such as remote controls are generally simple to operate. The main caveat to G scale, however, is that it is often much more expensive than other scales.
Space Factor
Another chief concern for the perspective set-up is space. Full-sized basements can accommodate elaborate G, O, and HO scale layouts. Such spaces allow for you to assemble landscapes, tunnels, roundhouses, and the like, will plenty of area to expand. But the smaller your available space, the smaller a scale you should consider. Also consider how much space you will have left to access your build to make repairs and right derailments.
Goals for your railroad
As with any hobby, you probably already have some idea of what type of model railroad setup you want to create. Whether it is a traditional oval or a do-it-yourself build filled with turns, tunnels, or slot-car crossings, there is plenty out in the market to build your own model railroad. You can even build one to be part of your home’s landscape or garden. It would probably be more satisfying to create your goals and then chose a scale to fit it than the other way around.
BUDGET
Unless you are constructing model trains to meet a business goal, you should keep your model train budget at the hobby level. Quality and brand are going to play a big role in your choices, so do your research before making initial purchases to ensure that the money you spend not only fits into your budget, but it also meets your age, space, and other goals.