Preventing split ends?

i just got a hair cut due to 2 many split ends. i have tried everything that is known to b best to prevent them. i have used olive oil, pantene beauty leanths, nexus spilt end repair, mane & tail shamp/condi. i am recenlt using miracle mane. i have dry straight hair & i wanna do my best to prevent them becus my hair next grows past my chest. i need sumthing tht will help prevent these monsters.& plz answer this only if u have tried whatever it is or has workd or knw some1 tht has used whatever and has workd plz help me out!! i am 16 if tht means anything. thanks -blacksheep