I need help

so i climbed my way up to gold from bronze 3 this season but just got demoted from gold for the 3rd time yes the third time i've been from S1 to G5 multiple times in the past couple weeks i'm gaining about 13 per win and losing 24 per loss and its seeming impossible to climb now my mmr is about 300 below the others in S1 and i need help getting back up. My kda isn't bad and i buy pinks every back if i have 75G but i just need help getting back up to gold is there any tips you could give me?