>>1973789>cassettes with large gearyes, but more accurately, for steep hills you want a LOW gear *ratio*
so, the "gear" you are in at any given time is actually 2 gears: a gear on the crank in front and the gear on the cassette in back.
so, yes, you want a big gear on the cassette but if the small gear on the crank isn't smaller than that big rear, it's not what you want.
for you: just starting, maybe a little heavy, and hilly terrain, I'd recommend you find something with at least somewhat lower gearing than 1:1.
a 1:1 ratio which is when the big rear and the small front are equal to each other . so what you want is a rear gear larger than the smallest front gear.
this is a common setup on cranks with only one gear, but there's nothing wrong with double or triple cranks, indeed they're usually more rangey overall. mtbs always have below 1:1 low gears because off-road is more demanding on the low end. it'll be common on gravel since they're for doing some off-road, too,
modern road bikes have much lower gearing than any time in the past but you may not see the gearing you want except on touring models, which would be cool if you wanted a roadie.
for a new bike, gravel is probably the sure-shot for your use case but get whatever you like. just get used to eyeballing the drive trains or you can look at spec sheets too. if , say, its a used bike and you can't tell by looking, most gears have the tooth count stamped into them somewhere. or just count.
also, for climbing, it is useful to grab the handlebars at the most forward position. drop bars bend forward from the stem and then grabbing the brake levers is the most forward position. flat bars are parallel with the stem but you can buy "bar ends" which will give an extension to make climbing easier, which I recommend.
