How I'd do it is have Favored Enemy have levels.
Favored Enemy level 1: +Wis modifier damage rolls to creature type or humanoid.
Favored Enemy level 2: +Wis modifier damage rolls and Advantage on Wisdom (Survival) checks to track creature type or humanoid.
Favored Enemy level 3: +Wis modifier damage rolls and Advantage on Wisdom (Survival) checks to track and Intelligence (Investigation) check to recall info on creature type or humanoid.
Favored Enemy level 4: +Wis modifier damage rolls and Advantage on Wisdom (Survival) checks to track, Charisma (Intimidation and Deception) checks to interact with, and Intelligence (Investigation) check to recall info on creature type or humanoid.
Favored Enemy level 5: + Proficency mod + Wis modifier damage rolls and Advantage on Wisdom (Survival) checks to track, Charisma (Intimidation and Deception) checks to interact with, and Intelligence (Investigation) check to recall info on creature type or humanoid. Learn the creature or humaniod's racial language.
At level 1, you get 1 creature or 2 humanoids at level 5. Each level you can gain 1 level 1 FE creature, 2 FE 1 humanoids, or increase 1 FE by one level.
During 1 month of downtime and some gp of resources, a ranger can research a FE and gain 1 level 1 FE humanoid or increase any FE by 1 level.
Favored Enemy level 1: +Wis modifier damage rolls to creature type or humanoid.
Favored Enemy level 2: +Wis modifier damage rolls and Advantage on Wisdom (Survival) checks to track creature type or humanoid.
Favored Enemy level 3: +Wis modifier damage rolls and Advantage on Wisdom (Survival) checks to track and Intelligence (Investigation) check to recall info on creature type or humanoid.
Favored Enemy level 4: +Wis modifier damage rolls and Advantage on Wisdom (Survival) checks to track, Charisma (Intimidation and Deception) checks to interact with, and Intelligence (Investigation) check to recall info on creature type or humanoid.
Favored Enemy level 5: + Proficency mod + Wis modifier damage rolls and Advantage on Wisdom (Survival) checks to track, Charisma (Intimidation and Deception) checks to interact with, and Intelligence (Investigation) check to recall info on creature type or humanoid. Learn the creature or humaniod's racial language.
At level 1, you get 1 creature or 2 humanoids at level 5. Each level you can gain 1 level 1 FE creature, 2 FE 1 humanoids, or increase 1 FE by one level.
During 1 month of downtime and some gp of resources, a ranger can research a FE and gain 1 level 1 FE humanoid or increase any FE by 1 level.