FVS318GV2 private subnet

Hi,

Here's my set up: 

Arris Surfboard modem < -> Negear FVS318GV2 <-> a couple of Airports (bridged mode) , some ethernet-connected devices, and of course some wireless devices. Currently all devices are on one subnet 192.168.1.1/255.255.255.0

I would like to put a a few wireless devices that I have assigned Fixed IPs to into a different subnet from all other devices. Let's call the subset "A" and all other devices "B". Both subnets need to be able to talk to the WAN, but not to each other.

I imagine this ought to be pretty simple, but I'm a bit of novice with this kind of router. Previously I just had simple wireless routers (Apple, Netgear, etc.) I think I need to:

1. Use VLANs to configure IP ranges and subnets
2. Make sure the devices are within those reanges (reserve the addresses for each device) ? I have also divided the devices into the LAN groups that mimic the organization I'm after but of course that by itself doesn't create separate subnets.

Anyway, if someone could suggest if I am close to the right approach or what I'm doing wrong, that would be a massive help. 

Thanks.