Help a noob route internet traffic from one interface to another

I've managed to set up an Edgerouter with a "management" interface on eth0, three VLANs on eth1 (eth1.20, eth1.30, eth1.40) and a PPPoE connection on eth2. I would like to be able to access the internet connection that's on eth2, on the eth1.20 VLAN and leave the remaining VLANs and eth0 isolated, without internet access.

Here's my configuration:

 interfaces {
     ethernet eth0 {
         address 192.168.1.100/24
         duplex auto
         speed auto
     }
     ethernet eth1 {
         duplex auto
         speed auto
         vif 20 {
             address 192.168.2.1/24
             description mate
             mtu 1500
         }
         vif 30 {
             address 192.168.3.1/24
             description tpg
             mtu 1500
         }
         vif 40 {
             address 192.168.4.1/24
             description skymesh
             mtu 1500
         }
     }
     ethernet eth2 {
         duplex auto
         pppoe 0 {
             password private
             user-id private
         }
         speed auto
     }
     ethernet eth3 {
         duplex auto
         speed auto
     }
     ethernet eth4 {
         duplex auto
         speed auto
     }
     loopback lo {
     }
     switch switch0 {
         mtu 1500
     }
 }
 service {
     dhcp-server {
         disabled false
         hostfile-update disable
         shared-network-name mate {
             authoritative disable
             subnet 192.168.2.0/24 {
                 default-router 192.168.2.1
                 dns-server 192.168.2.1
                 lease 86400
                 start 192.168.2.10 {
                     stop 192.168.2.20
                 }
             }
         }
         shared-network-name skymesh {
             authoritative disable
             subnet 192.168.4.0/24 {
                 default-router 192.168.4.1
                 dns-server 192.168.4.1
                 lease 86400
                 start 192.168.4.10 {
                     stop 192.168.4.20
                 }
             }
         }
         shared-network-name tpg {
             authoritative disable
             subnet 192.168.3.0/24 {
                 default-router 192.168.3.1
                 dns-server 192.168.3.1
                 lease 86400
                 start 192.168.3.10 {
                     stop 192.168.3.20
                 }
             }
         }
         use-dnsmasq disable
     }
     gui {
         http-port 80
         https-port 443
         older-ciphers enable
     }
     ssh {
         port 22
         protocol-version v2
     }
 }

I'm kinda at a loss at what to do - anyone got any hints for me?