Going from 2x8-speed to 1x11-speed I bought a beginner bike with a 2x 8-speed Shimano setup a year ago. I am looking to upgrade, now that I am getting more in to cycling then expected. Since I live in a really flat area (when I go on 3-hours rides, I climb less then 100 meters during the entire ride), I was wondering if I could manage with a 1x drivetrain? I would prefer this for the simplicity of it: price, weight and the reason I have never used my small chain ring outside (I do on Zwift, but I might dedicate my current bike to the indoortrainer).

I notice that when I ride outside (on my 2x 8-sp setup), I only use about 3 or 4 gears, and about 90% of the time I ride in the same gear. I do shift on intersections or when I encounter a serious headwind or a small hill, but that is only for a few seconds..

Could I enjoy a bike that has a1x 11-sp setup? And if so, how do I choose what casette configuration that I want? I am a beginner so I don't know what I need. I honestly don't understand all the 'calculators' online for gears. I THINK I want to have a few (maybe 2) low-low gears for hills and headwinds, and then maybe another 2 really high ones for (small) downhills or tailwinds. The rest should be closer to the middle, around where I ride now.  

Would it be ok to have big jumps in gears on both ends of my casette, and smaller jumps in the middle? Or isn't this possible or a smart thing to do? How would you advice I make a smart choice?

I don't have the means to buy a few casettes and experiment with them, funds are tight. 

Thanks
Yes, a 1×11 is a reasonable setup, especially if you live in a flat area. The weight savings is not that big of a deal, and I would not get a bike just because it had 1× setup if there were a 2× bike that seemed like a better option in other ways.

The theoretical ideal gearing setup would give you a broad range with the difference between each gear being a consistent percentage that's not too big, not too small. Say, 10% steps. This is not really possible because the steps in bike drivetrains are "chunky": all steps need to be an integer number of teeth, so some steps will be too big, some too small for this ideal.

The tightest 11-speed cassettes are 11-25: that spacing is super-tight, and mostly for racers. 11-30 or 11-32 cassettes are typical, and give you a reasonably wide spread. You can go wider (there are 11-50 cassettes) but the steps start to get so wide that it may be hard to find the right gear at any given time. One of my bikes has a 2×11 with 46/30 in front and 11-32 in back: I never shift out of the big ring, and very rarely use the biggest or smallest gears in back, riding on terrain with rolling hills, to give you a basis for comparison.

There have been cassettes made with a couple of extra-low bailout gears for hills, or one bailout gear and one super-high gear, but these are uncommon (they were made especially for the 3T Uno) and not all freehubs can fit a super-small gear. In any case, when you're riding fast, having closely and evenly spaced gears is more important than having one special gear for the jump to lightspeed.

It's worth coming to terms with gear calculators so you can understand what works for you and make more informed decisions. This one is the best one I've seen, because it gives you a visual sense of what's going on.