Bike specific clothing isn't about being a fashionista. If you wear good bike shorts, it cuts down on chafing. Jerseys help wick away sweat and keep you cooler, the back pockets can hold a few things. A regular t-shirt won't zip down the front and starts to feel choking around the neck.
Merino wool is very comfy. 'nuff said.
Good shoes help with keeping your feet warm and dry and have a nice stiff sole-- important if you use platform pedals like mine that have metal teeth. Regular tennis shoes are nice in hot weather because they breathe, but that's only 2 months a year where I live.
I personally HATE clothing that flaps in the wind. For me, sleeves need to be fitted. All that flappy flap is distracting. On short trips I like jeans and sweats, but hate them when they are stuck in my chain. On longer trips I hate jean seams digging into my skin. It's just easier to wear shorts or tights that wont get into the chain. I also like my long tights to have zippers at the ankle so they will go over shoes easily.
Bike specific clothing also has reflective strips sewn in which help with visibility. While not a need, it's a nice touch I like. Sure everyone can tell I'm fluffy, woo woo.
I hope you find clothing you enjoy and suits your needs. That's all that matters!!!