Recommend a dog breed (puppy) for first time owner?

Separation anxiety can occur in any dog, it isn't specific to any one breed. But there are ways to try and prevent this.

Whippets are gentle, non-aggressive and enjoy human companionship. Except they don't particularly enjoy the cold weather. They have the potential for joint issues, since they are such a slim / thin build with long legs. They are typically low energy, but can become overactive and destructive if their exercise needs are not met. They look very similar to a Greyhound, but are a bit smaller. They are natural family pets and are good with both small children and other dogs.

Shiba Inus are good-natured, alert, and bold. They are typically strong-willed and confident, and often have their own ideas about things. They can be loyal and affectionate with people, but tend to be suspicious of strangers. They also are known for not sharing very well, although this isn't true for all of them. Unfortunately, they do have a tendency to be stubborn and more difficult to train.

Basenjis are very affectionate with people, but can be nervous around strangers. They originally hunted in packs and are usually good with other dogs if socialized properly while they are young. However, some can be argumentative and snappy with others. Basenjis tend to be very clever dogs, but can be more difficult to train. But they are considered a "barkless" dog, since they tend not to bark very often!

Lagotto Romagnolos are described as playful and active. They are definitely highly intelligent and easily trainable. They are very loyal to their owners and families, but they are pretty aloof and not trusting towards strangers. They can make good watchdogs, as well. However, without proper training, they may end up barking too much. Lagotto Romagnolos are good at scent work, but they also have a natural tendency to dig. They are also extremely intelligent dogs and crave attention and stimulation for their attentive brains.

Good luck!