FortiGate in AWS

I'm trying to get a FortiGate setup and I have an outside subnet and an inside subnet setup on it.  From AWS, I have multiple subnets setup and wish for each of those to start going through the FortiGate. 

Can I set these up as VLANs on the FortiGate or do I need to enable a port for each one?  Currently, I have a medium tier FG setup, but it only allows me two interfaces, internal and external.

I cannot seem to get the correct configuration where I can have a test machine (instance) in a different subnet/VLAN where it will ping the FGT.

Example:

Outside: 172.250.254.254

Inside: 172.250.253.254

Test VLAN: 172.250.250.254 (IP for VLAN interface)

Test Machine 250: 172.250.250.250 (Linux instance)

Test Machine 253: 172.250.253.250 (Linux instance)

From Machine 253, I can ping the IP for the inside interface at 172.250.253.254.

From Machine 250, I cannot ping the IP for the VLAN 250 interface at 172.250.250.254.

On the Fortigate in cli, I can ping both the inside interface ip and the VLAN 250 interface ip.

I really can't find much in the way of how this can be setup with more than one subnet.