Honestly, that’s up to you. Bunnies are happier with friends, but they would be fine on their own with enough human interaction and play time. 

If you have enough resources, time, effort, and money, then go for it. I’m getting a baby for my 4 year old bun at the end of the month, the 4 year old is a boy and neutered. The baby is hopefully a girl, and will be spayed as soon as shes ready. 

Size doesn’t matter and age doesn’t either, as far as i know. I’ve read that, typically, male x female bonds do best. But same sex bonds aren’t impossible, and there have been many successful ones! 

Keep in mind that baby bunnies wont have much of a personality until their reach puberty, typically about 6 months old. And any time before that, they can’t be bonded to another bunny. 

The best option would be going to a local shelter and getting a bun from there. Typically they will come spayed/neutered, or they will spay or neuter them. Girls have about 85-90% chance of cancer in their uterus and ovarian cancer if not spayed after 1 year. If the shelters around you offer them, try bunny speed dates. The ones around me don’t, but everywhere is different.