How should I go about publishing my poetry?

I've been writing poetry for years and have decided to publish it so I started typing it all up onto my laptop and as i was doing so, I realized they fell into categories. Romance (usually teenage romance), really depressing emotive poetry, happy/inspirational poetry, nature/animals, and misc. I figure it would be cool if I could at least put all the dark depressing poetry and the happy inspirational poetry into a book and have it be like a yin and yang sort of thing especially since those poems are more where my heart and soul are. But I heard it's easier to get started publishing by just sending out individual poems to literary journals. I'm not sue how well that works with the whole category thing and I don't know where I would send some of these poems to. Another problem is that some of them are more relatable to the teen crowd because i wrote most of them in high school. I know there are many places to submit poems for teens but now I'm 21 so I think I missed my chance. Please correct me if I am wrong and give me some advice and name of publishers or literary journals I can submit to?