If you live in a hilly area, a wider gear range is handy. I always recommend a road bike over hybrids. Road bikes have greatly increased in popularity in recent years, and there are many options available in any price range. Get the best you can afford, and make sure it fits.

You seem to be going about getting started the right way. The lower gears don't take much effort do use, are less tough on your knees, and get your circulation going. As you get faster and stronger, you'll start pushing the taller gears more.

When starting out, it's important to get your bike set up, and properly set up for best comfort and efficiency. A bike shop can get you in the ballpark, you can use trial-and-error to get it just right.