I made gnometech.. and try to keep it simple.
I take a magic item and make it look like a steampunk creation. Such as boots of jumping and springing has Examples are
boots of jumping and springing that have small rockets on the side of the bronze/brass boots with a gooey (super rubber) sole. I sometime
I sometimes up the rarity and combine two items together, or give it some aspects of another item. Such as
Example: the above rocket boots also allowing a swimming speed.
Gnometech
Gnometech can also be just, more generically, magitech and I do. I have KoboldKobolds, Goblins and Dwarves with their own variations. It's a way to reskin an item to fit your campaign style better.