Equipment
Weapons are the bread and butter of your damage throughout Blade Idle. They have a base amount of attack plus a HUGE Attack% modifier, especially when you start using God-tier weapons.
Many roadblocks you will encounter throughout the game will be due to a lack of damage or ACU/PEN, so damage is significant. It is also essential for AFK farming so that you can receive more chests and rewards.
On top of this, each God weapon and Armor have owned effects at level 200, which are permanent. You must roll all Mythical or higher options for each slot to unlock this owned effect. Therefore you want to eventually level each God and Armor weapon to level 200 to unlock all owned effects.
Should I Merge My Equipment?
Weapons are used to upgrade your skills in Blade Idle, so you must ensure you have enough weapons to upgrade your skills, though they do not require too many resources to upgrade. Otherwise, you can almost safely merge your weapons and armor until you reach God-tier.
Weapons
You should feel a considerable power boost when you finally unlock your first God weapon.
God-tier weapons require many other weapons to upgrade them every 50 levels. However, once you upgrade them, they also unlock an option slot so that you can roll for bonus stats. Ideally, you want to roll for Option ATK% or ACU.
As you increase the grade and level of your weapons, the requirements you need to unlock other slots become very high, so you want to make sure you save enough Mythical/God-tier weapons strictly for upgrading God-tier weapons.
Armor
Armor is your key to survivability in Blade Idle. You need your chest pieces to increase your HP and Helmet to increase your DEF.
Generally speaking, DEF is more important than HP for your survivability, so if you ever want to upgrade your armor using enchant stones, focus on upgrading your helmets first.
Once you reach later stages where PEN and ACU become very important, your gloves will prioritize armor upgrades as they will most likely be the cause of your roadblock.
Since an update in early May 2022, armor items now have option slots, you can unlock. Make use of these slots. You must fully upgrade your armor to level 200, use some resources from previous armor equipment, and unlock all option slots at once.