Gems are stored on each individual tool part, making it possible to have 3 gems in total. The primary goal of gems is to improve the tools stat-wise. The gems will also change the appearance of the tool part.

Gems can be applied to tool parts in the upgrade station.
Gems can be upgraded to a new level in the upgrade station.

Handling the state of a tool part can be challenging when its state get complex. The tool part has to take into consideration material + secondarymaterial + type of tool part + possible gems. In which order should effects be applied? IDK yet. I might look into implementing a system for handling state on each and every tool part.

Using the state pattern might be a good idea.

I need to create a system for creating and managing possible gems and their stats. I also need a system for registering gems an their connected items.

I need to handle custom textures and create support for their models.