I use Manual or Sports Mode on my Canon EOS 750D.
Hi, ok, for a start, using manual is a surefire way of making your life more difficult, and sport mode is just a Canon aid to users that that don't really want to learn anything.
Fortunately, you sound like you do, because your asking for help
Photography works on a triad of things, aperture, shutter speed and film sensitivity (or ISO in digital speak).
Aperture is the f number on your lens, on a kit lens, like the 18-55mm your f number is f3.5 at the widest 18mm focal length, and f5.6 at its tele 55mm focal length. The lower the f number, the larger the aperture and the more light gets let into the camera.
Shutter speed, is the exposure time, the longer the shutter speed, the more light comes in, but the longer the shutter speed, the more prone your camera is to shake, which makes for blurred photos.
ISO (sensitivity) again, the higher the ISO, the less light you need, but be careful, going too high on ISO makes for grainy photos.
So, in basic terms, you need maximum light, so low f number, with a shutter speed that prevents shake or blur and a high enough ISO to maximise sensitivity whilst keeping the photos from being grainy.
For ease, I'd pop your camera into Aperture priority, set your shutter speed and ISO to auto with a cap on say ISO800. Then push your f number down as low as you can and as wide a focal length as you can. Once you start getting keepers, start working with higher f numbers and more tele focal ranges.
Your lens will have IS (image stabilisation) this will give you on a 18-55mm lens about 3 stops of stabilisation, or in real terms, allow you to use either a longer shutter speed or lower ISO or higher f number than without IS, always switch it on unless you are on a tripod - lenses typically detect you are on a tripod anyways, plus, it won't break anything.
Make sure you have AF-Servo set on your camera, you get this via your settings on the back, this will allow continuous autofocus as the train approaches, as you half depress the shutter button, increasing the chance of a in focus shot.
Last, try to shoot with as much ambient light as possible, firstly in daylight, then gradually as you get more keepers, try shooting in lower light areas, at dusk or on stations at night.
I'd recommend a book called "Understanding Exposure" it's about £15 on Amazon but helps understand another principal of photography - depth of field
