on a triple; middle or big ring at the front, and then just find something on the back you’re comfy with. changing gear is easy and you will do it a lot and end up not even thinking about it.
the levers on a triban 3 are a bit weird and unlike those on a newer road bike as they have a thumb lever for changing down (or up, can’t remember, to do the inverse you move the entire shifter inwards)