What brand of straightner do you recommend for my hair?

I have medium length wavey hair and I spent about 50 dollars on my hair straightner about 2 years ago and it just doesn't work on my hair it takes me like 45 minutes and it goes wavy when I just sit and eat for 15 minutes. And my friends have longer hair that's wavy and she said it on takes her 15 minutes to do her hair. And I have thought about just paying for a chi because my friend likes hers but is there anything else that could possibly be cheaper but worth my money?