Hair Straightener

My hair is super thick and curly but I want to straighten it. I’ve had a professional straighten it before but I’m sure they have super expensive straighteners. My hair is so curly that if i straighten it it usually curls back up with in a few hours except for the one time my hairdresser did it. Any suggestions on which one I could buy so it fully straightens my hair?

My hair was wet in this pic

Lol old picture of me

My bestie and I on homecoming! I’m the one in blue (hopefully you can see my hair)