Below is a table of upgrades in tiers of importance for Town Hall 4.

Tier 1Add all new traps, defenses and buildings.
Laboratory to level 2.
Tier 2Clan Castle to level 2.
Army Camps to level 4.
Tier 3Elixir and Gold Storages to level 8.
Elixir Collectors and Gold Mines to level 8.
Tier 4Barracks to level 6.
Air Defense to level 2.
Tier 5Max remaining defenses and upgrade your Town Hall to level 5!

Try to keep your walls on par and maxed before upgrading to Town Hall 5. You don’t want to drag behind this early in the game!