Hiya quinn, long time no see!
I'm right there with you, a baby gardener asking a ton of questions (and getting some really good answers!)
This is also a specific question I've researched -- I like perennials, and the existing bloom in my yard tends heavily towards spring, while I want some later stuff too.
I really love hydrangeas -- they're late-bloomers, perennial, and like a variety of exposures of sun (see, you can tell I'm new to this, I dunno how to categorize the whole "part sun" or "part shade" or whatever labels).
They also come in a variety of colors, and you can even adjust the colors on several of them by putting stuff in the soil.
I also just planted some toad lilies, I love 'em:
They're late-blooming, perennial, and like shade.