VLANS - Newish to VLANs, looking for some advice

Hello. I have a GS728TP and I have it connected as follows....

.....the router connects to the Netgear switch into port 1. 

.....into port 9 I have a few computers plugged into via another switch at their end, all on VLAN 50. But VLAN 50 cannot get access to the internet. What is it that I'm missing in giving VLAN 50 internet access, whilst still ensuring no one else can get into that VLAN?

Thanks.