What would be the first modification i would need to do on my E&C Glock 17 Gen 5
 

Just wanting to know

Likely none... use it first and learn to handle it. Then compare it against other players' pistols. After a while, and with experience, you will know if anything needs to be improved.

My stock kwc 1911 with .3's is an absolute monster.
What drakker said, test with different weights, adjust hop, get it where you like it, then debate upgrades from there

:):):)

add a return spring bushing. i 3d printed mine. they're notorious for sticking when racked