Gray blazer to class up casual outfits

[marooooon]

Hey Styleforum, I've read this forum every now and then and just decided to join you guys officially. I was hoping you guys could help me out with my next purchase.
I'm a college student in the market for a gray blazer/jacket, which would be my first one. I dress pretty well for the casual college setting and I think this would really add an extra something to my outfits on nights out. I'd be wearing it with dark brown oxfords and dark skinny jeans or maroon skinny pants. I'm a skinny guy (5'11", 135) and my look is definitely oriented to the slim fit.
I feel like I know how it should fit (lined up with the shoulders, flat on the back, little slack in the front, showing some cuff) but if there's anything specific I should look out for to guarantee a nice fit, I would appreciate the heads up.
I'm looking for advice on what to look for or avoid as far as features go. Obviously single-breasted, but one button? Two? And how about lapel? Material? Light/medium/dark? I'm thinking medium.
I've noticed that people here say to avoid ones that "look like an orphaned suit jacket." Could someone explain this idea to me and what kinds of jackets I should avoid to follow this advice?

I had the pants already and this picture is kind of what inspired the desire for a blazer:

Thanks a ton. Stay classy.

 

[acecow]

Get one from a thicker material, not from smooth wool. I have a gray camel hair jacket which looks lovely with pretty much anything casual, especially jeans. Here's an old fit of mine with that jacket:

You are young, so probably don't want it to be classically long. Depending on your build, unless you have unproportionally long legs already, have it end before covering your ass in its entirety.

Also, patch pockets would help to make it more casual. If I think of something else, I'll post more suggestions.