Ask HN: Product development guidelines, best practices and other question?

Been doing a different kind of evening project the last months, actually designing and developing a physical device/thing, sure it will have microcontrollers on it, so some programming was done, but now Im kind of stuck.

How do you take your prototype, your assembly of parts from aliexpress/China, into a nice package, plastic containers and looks, and into producing a first batch say 100 or 1000 pieces?

What the product is, is actually an integration/collection of about 10 different general parts, and I need to make a few of the parts much better looking - placing them inside white shiny plastic cases, making better connectors and such. How do I do that, where?

The price range for the final product is 199-249usd, its like a premium/apple-style "best white looking products" of its kind.