Did anyone has any experience on replacing normal spokes with those more aero such as DT Swiss aero , sapim cx-aero?
My wheelset used for training are the Campagnolo Khamsin G3, i was thinking to replace the spokes of the front one in case i need to setup my bike for criterium races.
I own a pair of 50mm Aero wheels but in some cases a lower profile at the front will help a lot to control the bike and in theory the aero spokes will made the wheel more aero...

Do you think i can improve the wheel for real or is just something good "in the paper"?

Minimal aero gains aside....you have boutique wheels with spokes/nips you get from Campagnolo....if you were to actually rebuild these wheels, you'd have to first ascertain if anyone other than Campagnolo made spokes and nips that would even fit in the hub and rim-Some years Khamsin was straight-pull others were J-bend. Khamsin being low end--the odds are better, at least compared to Fulcrum 0s that have bizarro spokes no one else makes.

Also...Wheels retailing for $300 new...unless you do this this yourself--the cost will just about what the wheels are worth in parts ($150 for spokes/nips) and manpower ($100ish for 2 wheel rebuilds)....for TBH dubious gains.

Thanks! The cost of the spoke where around 30€ per wheel plus the service.
Basically the gains do not worth the cost.