How to keep price as low as possible when you don't know electronics

I had an idea to create a microcontroller based computer.

I have no in depth understanding of electronics, I'm a website designer, delving into embedded  microcontrollers.

So I had an electronic schematic design made (eagle kikad whatever you call it) based on my requirements, where I relied on the designer to guide me as he was the experienced one.

I was sent the gerber files and a pdf of the schematic and now the designer is not responding to messages.

I would like to identify the parts in the BOM list so I can source them on *** (use the *** part numbers) as I understand they are the cheapest.

Some of the components in the bom file have no values, maybe if I knew about electronics I could find out from the schematic?...

I wanted to order 20 assembled units, but am kind of stuck half way through a project having already paid the designer for his work and none the wiser really.

I'm sure there have been many people in this position before, and wonder how they resolved it... As for me, I cannot seem to find a straight forward way out since the descriptions of the components are quite broad like "capacitor american symbol" so googling stuff doesnt help really.

Thanks for reading.