Blend ingredients until smooth. Chill for several hours before serving.
While this recipe seems simple, there's a lot of room for customization.
First, the seasoning. Ranch dressing mix packets haven't fully died out, and they cut a lot of the hassle out of making your own ranch. If you'd like to use your own spices, that's fine. I've got a rough guide below to how to make your own ranch dressing mix without needing to buy a paper packet each time.
Second, there are a LOT of things you can do with the peppers. I'm a fan of using a mix of toasted jalapenos, habaneros, and Anaheim chiles. If I'm careful to seed all of my peppers completely and I use mostly Anaheim chiles, the ranch comes out pretty spicy but not too overpowering. If I use mostly habaneros and let a couple of seeds through on purpose, I'll get a sauce that's crazy high on the spice-o-meter.
Feel free to use whatever peppers are handy in your area and adjust the recipe to your own taste. As a rule, more seeds = more spicy. Buffalo Wild Wing's ranch is pretty spicy, so if you're looking to emulate that you might want to start with well-seeded jalapenos and go from there.
I mentioned this in the ingredients section, but low-fat mayo or sour cream will NOT give you the taste or texture that you're looking for. Ideally, you'd actually make your mayo yourself, but if you're not willing to break a few eggs, look for real, full-fat mayo at the store. Same thing with the sour cream. You want plenty of decadent flavors in your final product.