Question

Meaning of always classy, never trashy and a little bit sassy.

Answer 1

Always classy means being well groomed, neat, elegant and at the same time sophisticated

Never trashy means that once someone decideds to be classy, they should avoid to be overtly sexual in they way they present themselves. Being polite rather than being rude. In short having a sense of dignity in the way you dress and speak.
On the other hand being sassy means being bold and full of spirit in such an attractive way.

Therefore, this satament simply means that one should do everything without any exergarration but just have the right touch of everything

Answer 2

To be classy means - to be stylish and sophisticated; Trashy means - of poor quality, especially regarding the items of popular culture or fashion; being sassy means - to be lively, bold, full of spirit, and cheeky.

So, the popular quote "Always classy, never trashy and a little bit sassy", means to be sophisticated and elegant always and never be poor minded or low quality while being a little bold and with high spirits.

Usually, the quote is used in the fashion and trends sense apart from being used for nature and personality depiction in a casual way.