Upgrading crafted gear

i have a 420 crafted wrist that I had crafted with an embelishment. I have a spark. I don’t have any +recipe items.

how do I upgrade this in the crafting system?

I don’t feel that I understand what ilevel a crafted item will be when i put it into the crafting system.

Is it based on my mats or on the crafter’s skill level? Something else?

Just recraft/submit recrafting order (I would find a craftsperson as opposed to making a public order), and provide the mats for the recraft.
Use higher/est quality mats, and find a crafter with maxxed skill/spec for best results. Depending on difficulty, you may need to have them (or you) use an Illustrious Insight for extra skill.

You sort of can’t, unless you know the crafter’s skills/specs, and even then not sure if you can see it. You can specify min quality on personal orders, that’s why I suggest using them as opposed to public for recrafting.

Both, and their spec can increase skill/inspiration.

It will cost some resources, but not as much as crafting from scratch.

However, it is just a new roll, it does not guarantee improvement. In fact, it can even result in a lower quality item if mats/crafter are worse than the original or you are attempting to add new embellishments that increase the difficulty.