I don't have any Blazers or anything tailored except 1 nice light grey suit. What to do. I am stressing out.
Please help 😕
Honestly, I have no idea, since "semi-formal" in 2015/2016, has virtually no meaning. The classic definitions of "formal"=tails and semi-formal=tux/dinner jacket has been gone forever. "Formal" today means tux, and "business" is obvious, and enough people have figured out "business casual" that there are standard uniforms. "Semi-formal", however, is hard to figure out. Maybe it's best to ask the host wtf semi-formal means for his/her event.
A solid, navy tie, would work better for an evening event. That tie, with that suit, is pretty business-y. A solid would work better for NYE.
As for the dark shirt, light suit, idea. You see pictures of George Clooney, and he generally looks pretty good doing this, especially sans tie. It also worked on Vincent D'Onofrio's Kingpin in Daredevil. But most of the time, you'll end up looking like a low rent pimp who bought his entire outfit at one of those places where you can get 2 100% polester suits (shirts and ties included) for $150.