This setting follows the "Ancestry & Culture 5e" ruleset for D&D 5e. When choosing an Ancestry: ignore predetermined ability score modifications. Instead, each character has one "predominant" ability and one "secondary" ability that you feel represents your character's background and growth so far. A predominant ability score receives +2 at first level. A secondary ability receives +1 at first level. All other applicable cultural and ancestral abilities and features are then applied to your character, and can be modified via collusion with your dungeon master.
When choosing a class, pick from any official, published D&D 5e class. The revised ranger is also an acceptable class choice.