The best way to find out what breed is the ideal one for you is to read about as many dog breeds as you can, their breed origins, and what they're bred for. If you're considering a mix, make sure that you learn about each breed included in the mix. A great place to do so is the American Kennel Club website. You will find on there that each breed is displayed with its history and traits but also categorized into different types of groups (Sporting, Working, etc). All of which are key details to take into account. In a way, these overall but important details may prepare you for the type of dog you might get but don't forget that dogs are also individuals, and it's very well possible that you might end up with a dog whose personality completely contradicts everything you've learned! This is all simply part of the fun when bringing a dog home.
Another place to learn even more about a particular dog breed is breed-specific Facebook groups, as you will be able to ask questions directly to pet parents that live (and sometimes breed) the breed you're interested in!
Lastly, take into strong consideration what your lifestyle is, as well as the mental and physical requirements of each breed. The common mistake I see pet parents make is they primarily focus on the aesthetics of the dog (including whether they are or aren't hypoallergenic) or if they're considered family/child-friendly, when they should first and foremost be focusing on everyone's interest to match the potential and drive the dog or puppy their bringing home might come with. Whether you're considering a small or large breed, a puppy, or a rescue, each breed has its own traits. And these are traits that you will not be able to train out of them, but that you will rather want to make sure you provide outlets and encouragement for, in order to best fulfill your dog's needs so that they can then have a happier time giving you everything you want.