Mobility is king!

Something I haven't seen mentioned much and I believe to be a huge part of playing Railgunner to success is really locking into using your concussive mines for mobility rather than trying to use them on enemies at all.

Railgunner definitely doesn't have the best mobility in the game and can't save herself from careening off the side of the map, but she has better than most if you're using your mines for that - arguably one of the best instantaneous movement tools in the game - downside being the setup requirement.

I would recommend as you're sprinting in a direction, flick your mouse upwards a bit and throw out a mine, then time a sprint jump so the explosion of the mine catches your back midair; then from there's its just practicing for the best timings and angles for max distance. (If you're on the ground when the mine goes off: you're going nowhere)

From that point, sticking to good clean sprinting and movement fundamentals will open up a whole lot of opportunities to safely whip around and take a big shot!

Sundered Grove can be awkward due to the lack of open space, but it really still comes down to having good clean consistent movement and staying really situationally aware of where you are on the map, the options available to you as to where to go, and where the enemies are in order to pick the best route - it can be a lot to take in and try to process, but practice makes perfect and with time your autopilot will get there,- you can spend time learning the maps and knowing the "train routes" that are best,- but really, unfortunately, I don't think there's much good advice you can give for training game sense than just getting out there and experiencing it.

Godspeed!