LAYERSSSS! i LOVE layering a long sleeve under a shorter sleeve shirt, it adds some dimension. its extra good if the shirts are different lengths/necklines are different widths, it gives more texture peeking through which is yum!
adding simple accessories is great too, one thing that i find makes an outfit so much better is adding a necklace. even if its a plain chain or two, it adds some little bit of extra something special that's really good. i also like studded anything!!
one last thing i feel is you cant be scared of how you look, ive noticed the confidence is easily half the outfit. plus you dont want to be scared of trying things out! mix patterns and textures even if you aren't sure youll like them together, it doesnt hurt it to put it on and test it out just to see!