The sneaker is now officially a fashion category for footwear (hooray), so you should plan to add one to your shoe closet just as you would a new heel or sandal.
There is, however, one decision to be made, and that's which kind to snatch up. Would a more athletic-looking trainer suite your style best, or would something a tad more minimal be a better fit? The sportier version is a little trickier to style but works well with clean separates like a cropped skinny pant and boxy cotton shirt. The slide can be treated like a flat and looks best with pleated skirts and more feminine separates.
If you can't decide, don't worry, there may be a way to add both! Since traditional sneakers brands are adding street wear styles, the prices can be very pleasing. The easiest intro is, of course, to start with black, grey or white sneakers. They look fresh when mixed with unexpected pairs like a colorless pastel coat, button front shirt, and graphic print full skirt. The overall feeling should be sporty, but not gym attire - definitely skip the stretch pants.
Remember to keep the rest of your accessories looking styled by adding a great pair of shades, a stud earring, and a structured bag. Mixing trendy items with your investment pieces is always a good formula to follow.