Should let my hair grow even longer, or get it cut soon?

If your hair looks bad how do you know if what it needs is to grow longer or get cut? My longest lair is slightly below shoulder length. And my lairs are too far apart. I have three layers. My haircut looked good at first when it was straightened, but then I eventually got grounded from my straightener, and when my hair is not straightened the haircut that I got doesn't look good on me anymore. My hair is wavy when I blowdry it and almost curly if it airdries. Plus I DON'T look good with CURLY hair. But lately I've also been trying to avoid heat products because The ends of my hair were starting to get dry. My haircut looks EXTREMLY different when it's not straightened! You might think I'm exagerating but I'm not. I thought about maybe dying my hair darker and thought that it might make it appear less curly/wavy. A lot of people told me that all it needs it to grow. but I'm not so sure about that... Should I let it grow even longer or get it cut super short? I can't afford hair extensions. And yes by short, I mean as short as most guys have their hair. (I'm a girl).