Below is a table of upgrades in tiers of importance for Town Hall 6.

Tier 1Add all new traps, walls, defense and buildings.
Laboratory to level 4.
Tier 2Army Camps to level 6.
Clan Castle to level 3.
Spell Factory to level 2.
Tier 3Barracks to level 8.
Elixir and Gold Storages to level 10.
New Elixir Collector and Gold Mine to level 10.
Tier 4Air Defenses to level 4.
Air Sweeper to level 2.
New Air Bomb to level 2.
Archer Towers to level 7.
Wizard Towers to level 3.
Mortars to level 4.
Giant Bomb to level 2.
Cannons to level 7.
Tier 5Town Hall to level 7.

Try to keep your walls on par and maxed before upgrading to Town Hall 7. You don’t want to drag behind this early in the game! And at Town Hall 6 you don’t need to worry much about your War Weight and the order you upgrade your defense.