Wired Intelligent Edge

Example network:

1 x L3 switch

5 x L2 switches connected to L3 switch

Switches contain various VLANs with the following IP's assigned on the L3 switch:

VLAN 1 (Default VLAN) = 192.168.50.0/24

VLAN 2 (Servers) = 192.168.60.0/24

VLAN 3 (Clients) = 192.168.70.0/24

VLAN 4 (VoIP) = 192.168.80.0/24

Which of those VLAN's/IP's would you set as the L2 switches default gateway address?

Honestly, It all depends on which VLAN you want to manage them from - or to group them together with other network devices. It's really your choice.