The free Hypervisor doesn't have any restrictions regarding networking, except for using a distributed switch which is only available with an Enterprise Plus license.
Separating the storage network is recommended, and you don't want/need to set a gateway IP address for this since routing isn't supported for storage traffic anyway. The only VMkernel port group on which you configure the default gateway is the Management Network.
>>> I cannot set my own network range when creating a new vswitch
A vSwitch for virtual machine traffic doesn't have it's own IP address. Network settings are configured within the guests only, except for VLAN tagging, if you are going to use this feature.
André
