For that budget you should look for used parts.
I think for Eastern Europe you should use Ebay.de, but you may have a local used marketplace that is cheaper.
An i5-4570 is still an excellent CPU and will perform well in modern games. I use one in my HTPC along with a 1660 SUPER and it achieves solid 60FPS in most games. You can expect to find one for approx 40 euros, e.g:
https://www.ebay.de/itm/224517365329?hash=item3446471e51:g:NmkAAOSw8c1g03B6
The best motherboard for an i5-4570 would be an ASUS board with the Z97 chipset, e.g;
https://www.ebay.de/itm/194215600622?hash=item2d3826e1ee:g:-3oAAOSwlPNg1WZc
This board takes DDR3 and has all the modern features you would want. Expect to pay around 100-120 Euros for a board in good condition.
Although these are older parts they are still more than capable of playing the latest games at a professional level (with a good GPU), and of course Web App development tasks will be a breeze for this CPU / Board combo.