My experience is that when I started riding a year ago I was pedaling at around 60 rpms - typical for a brand new rider. I now pedal around 80-85 rpms comfortably. You get used to it. Pedaling in a lower gear and higher cadence is definitely less tiring, especially when doing longer distances - but you'll get there. If you don't have a cadence monitor, you can just count how many times your foot goes past 6 O'Clock for 30 seconds and multiple by 2. that's your rpm. Experience what feels right for you for now- later when you've ridden more, try an easier gear with a little faster pace - but most of all, have fun. I try not to turn my riding into a stressful event full of "shoulds". It all comes in time if you stick with it. At least that's how it is so far with me.