Cyberdimension Neptunia: 4 Goddesses Online (EP)

The easiest equipment I found to upgrade was Neptune's first sword of the game, the Longsword as both upgrades require common ingredients found throughout the early dungeons. If you're somewhat thorough with your explorations, you can unlock this early in the Guild Rank 2 missions, which is required to unlock the Blacksmith. Once you do, you can upgrade the sword, which will unlock this trophy.
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Upgrade it once more to unlock the following trophy: