A cami or a training bra?

When should I start wearing a training bra? Do I need one yet? I play volleyball and so I have a thin shape and I want to get one at the right time to get the best amount of training. I live with my aunt, uncle, and 2 cousin boys, so yeah, I want to not make it a big deal just go to the Old Navy across from middle school. If I measure, I'm 27 under and 27 1/2 around. I don't want to make a big deal about it, and I want to go to the store myself. Like maybe Old Navy?

Thanks!♥️

A cami or a training bra?
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