I'm setting up a new campaign setting at the moment and have made room for all of the PHB races as well as Goliath, Genasi, and Aasimar. Classes are all in there and if anyone wants to play one, the mystic is also available. I'm going to make the magus class found on the DMs guild available as well. It's actually been fun locating all of the races and classes in the world. For classes, some are found everywhere, but for others, you can add them into the world building.
As an example, I have monks with certain subclasses set up at different monasteries. The elemental monks only monastery is down on an island in the south; open hand monks have monasteries in multiple places and are quite common; and no one knows quite where the shadow-monks come from but speak of them in whispers. Of course, some players that play monks may not want to come from some island monastery so I have travelling masters roaming the country training students who show promise as well.
For races in my new setting. The 3 races of elves live together on (and in, in the case of the dark elves) a plateau that they have turned into a forested paradise. Dwarves have their typical dwarven vault in the mountains to the north. Gnomes are found either with the elves or with the dwarves depending on the subclass: Forest gnomes with elves, rock gnomes with dwarves.
I'm definitely having fun setting it up, I hope my players enjoy it.