i may be a little late chiming in here but you can build a super low end gaming system for about 400 to 450 USD probably about 360 to 400 euros
i'll share a build here. this one's less than 300 before shipping and tax but you can swap a R5 3400G in easily and later add a graphics card if you need.
https://secure.newegg.com/Wishlist/SharedWishlistDetail?ID=zWBzDUxKXyNoeF0jdpSPxg%3d%3d
EDIT: Don't forget to flash the BIOS First though on the MOBO to work with 3rd gen Ryzen.