Upgrade priorities at Town Hall 8 varies slightly depending on your focus on war or farming.

War FocusFarming Focus
Tier 1Build Dark Spell Factory.
Laboratory to level 6.
Clan Castle to level 4.
Build Dark Spell Factory.
Laboratory to level 6.
Clan Castle to level 4.
Tier 2Barbarian King to level 10.
Build new Elixir and Gold Storage.
Build new Dark Elixir Drill.
Build new Dark Barracks.
Dark Elixir Storage to level 3.
Build all new traps, defenses, buildings and walls.
Tier 3New Dark Elixir Drill to level 3.
New Elixir and Gold Storages to level 11.
Elixir Collectors and Gold Mines to level 12.
Dark Elixir Storage to level 4.
Barracks to level 10.
Dark Barracks to level 4.
New Dark Elixir Drill to level 3.
New Elixir and Gold Storages to level 11.
Elixir Collectors and Gold Mines to level 12.
Dark Elixir Storage to level 4.
Barbarian King to level 10.
Tier 4Air Defenses to level 6.
Air Sweeper to level 4.
Air Defenses to level 6.
Air Sweeper to level 4.
Hidden Teslas to level 6.
Giant Bombs to level 3.
Skeleton Traps to level 2.
Wizard Towers to level 6.
Archer Towers to level 10.
Bomb Tower to level 2.
Mortars to level 6.
Cannons to level 10.
Tier 5Build all new remaning traps, defenses and walls.
Get them on par with Town Hall 7.
Bombs to level 5.
Spring Traps to level 3.
Barracks to level 10.
Dark Barracks to level 4.
Tier 6Hidden Teslas to level 6.
Giant Bombs to level 3.
Skeleton Traps to level 2.
Archer Towers to level 10.
Cannons to level 10.
Town Hall to level 9.
Tier 7Bombs to level 5.
Spring Traps to level 3.
Wizard Towers to level 6.
Bomb Tower to level 2.
Mortars to level 6.

Tier 8Town Hall to level 9.

It’s highly recommended you max your walls and Barbarian King before upgrading to Town Hall 9 where the real wall and hero grind begins!