How much should I spend on each component on a 650 euro pc?

It should:

HDD or ssd / m.2

600w power supply

GPU and CPU

8gb ram

And all of this should go into the tech infinity micro atx housing which costs around 65 euro.

I'm playing:

Warframe, gta5, fortnite, apex, warthunder

Definitely buy 16gb ram for a 600 euro pc.

OK

You don't need a 600w power supply for a 600 euro PC. Better to invest in RAM.

Don't buy 8GB RAM, far too little and more suitable for a work PC than a gaming PC

To upgrade