I love the last one. Don't want to say tights cause that makes it seem like that's all I care about. But it has a conservative but free look to it. Wouldn't be able to tell you except with a simile. Like someone who dresses to a job interview looking professional. But ends up making everyone turn their heads at the same time.
I'd say nr 3 or 4. In look nr 4 I think the pattern of the tights is a bit "overkill". Simple sheer black tights would be better I think. Look nr 1 is nice in general but the top is so flowery it dominates all the rest.
Well the one with the tights is probably the best. I would suggest with any crop top to wear high waisted pants and with the open cut out back probably wear a bandeau with it or sports bra so people don't see your bra. Also maybe pair the floral skirt with a cardigan or a shrug. :)