What would make me a more hirable teacher (or give more job security) being certified in 2 subjects or a Master’s in one? (For 6th-12th)?

I want to become a teacher. Ideally I’d like to be able to teach K-12, but while being more expensive I feel it would also take too long since I’m already in my 20’s. I also already have a Bachelor’s degree in an unrelated field (advertising). I’m currently a PALS Tutor in an Elementary school, while I enjoy working with those ages I’m leaning more (currently) towards the middle school and high school ages, if I have to choose (though I’m having a tough time really choosing). I do also volunteer working with teens in a church setting around four times a week. I really want to teach history but if I taught two I’d also like to teach English.