Identifying components on circuit diagram
Different capacitors are for different purposes, and thus are of different types and different capacitances. C1 and C4  are for power supply filtering. C2 and C3 are load capacitors to the crystal to make it vibrate at the right frequency.

D1 and D2 are diodes. We don't know any more about them than you do. Most likely almost any standard small signal would do, but I will not suggest any type so I am not responsible if it damages your computer.

That is not an oscillator. That is simply a 12 MHz crystal. It does not have 1 coulomb charge, crystals are labeled Q and thus first crystal is Q1. The other parameters are unknown. Based on the 27pF capacitors, this crystal must have load capacitance rating of at least 13.5pF, perhaps 16pF to 20pF.


Beware that this circuit is rather tricky and the AVR actually has no hardware support for USB. If you must build it yourself, beware that any mistake can damage your USB port or whole computer permanently. I would not use thiäe above circuit myself or recommend it for any purpose. Better spend the approximately $20 amount of money on something that is a ready built board with much more capable MCU with hardware USB support, such as many of the STM32 Nucleo boards.