I don't mean to be glib, but there isn't one.
CPU, even with APU
Motherboard
RAM Storage
GPU if needed
Case
Decent PSU
ODD
OS
Come to well over 300 euros.
you best chance would be a refurbished Dell OptiPlex with an old i5, off lease and to put a 65W GPU like a 250 or GTX 750 ti in it.