This is my second season cycling. I live in an extremely hilly area and last season I got to where I could climb the steep hills without getting out and pushing about halfway through the season, but long and gradual hills absolutely murdered me. This season I started tackling some long gradual hills
Honestly you have to play with the gearing to find what works well for you on hills. Higher gears spin harder but put down more power, lower gears spin easier but put down less power. Best is to be in the highest gear you can sustain. Personally I never touch the lower half of my gears because there’s just too much leg spin and I tire myself for nothing.
Eventually you’ll get to where you can stand on the pedals while at a low cadence for extra power (useful on hills or with a trailer. When I have my kids behind me by butt basically never touches the saddle) but ultimately it’s something that takes building muscle and practice to get comfortable
I read an article forever ago about a place in Tibet that wasn’t on the grid and had pedal chargers for some laptops at a computer cafe