You can enable "gesture backlight" so that it lights up when you rotate your wrist to look at it. This is under your general settings, backlight area. Toggle it "on". This will help. You can also adjust the backlight amount but you can't adjust screen contrast or brightness which I find a bummer, to the default "no backlight" resting screen.
You can also adjust the level of the backlight. The factory default is 20% IIRC. Settings>system>backlight, then during activities or watch mode.
These are reflective screens, so in bright light (sunlight), very easy to see, but as it gets darker, a bit harder. The choice of colors on something like a watch face can help too. But it's part of the reason the watchface can always be on, and you get incredible battery life.
