If you see a warning when you acess one PC from another one in the same network, the network setup on the PC must be wrong, maybe it has subnet 255.255.255.0 ?
If the networking is correct, the 192.168.2.15 should not need the gateway to access 192.168.0.14 or 192.168.0.3.
Those PC´s should have netmask 255.255.252.0