There are no shortcuts, it's about building the legs, and lungs, and body. There may be some factors that could make it a little easier, but the main factor is getting strong enough, which takes some time and some dedication.
Probably going to the easiest gear is not the best choice as it can make a climb endless. Try to get into the hill at good speed, with your legs cycling at a comfy cadence, not like a windmill, and then try to maintain that cadence, when it gets hard you can either step up on the pedals, or go to an easier gear, maybe do both un that order... But keep doing it, maybe do some leisure rudes that have some climbs that you can do, and go up those... It's about getting your body used to it mostly...