I have been testing some lvl 30 (max) enchants for all tools. Here are the results, more coming soon!

Helmet
Test 1: Protection 3
Test 2: Protection 3
Test 3: Fire Protection 4, Aqua Affinity 1

Chestplate
Test 1: Protection 3
Test 2: Projectile Protection 4
Test 3: Projectile Protection 4

Leggings
Test 1: Fire Protection 3
Test 2: Protection 3
Test 3: Protection 3

Boots
Test 1: Fire Protection 4
Test 2: Protection 4
Test 3: Protection 3

Pickaxe
Test 1: Fortune 2, Efficiency 3
Test 2: Efficiency 4, Unbreaking 3
Test 3: Fortune 3

Shovel
Test 1: Unbreaking 3, Fortune 3, Efficiency 4
Test 2: Fortune 3, Unbreaking 3, Efficiency 4
Test 3: Efficiency 4, Fortune 2

Axe
Test 1: Efficiency 4, Unbreaking 3, Silk Touch 1
Test 2: Unbreaking 3
Test 3: Efficiency 4

Sword
Test 1: Sharpness 3
Test 2: Knockback 2, Sharpness 4, Fire Aspect 2
Test 3: Knockback 2, Sharpness 4, Fire Aspect 2

Use these stats to see what to enchant now, and what to save for later!
Hope this was helpful!