What ports do I need to open to permit VPN traffic?

For PPTP VPN connections, you need to open TCP port 1723 (for PPTP tunnel maintenance traffic). PPTP also uses IP port 47 for tunneling data. Port 47 is designed for "General Routing Encapsulation" or GRE packets.
For L2TP VPN connections, you need to open UDP port 500 for Internet Key Exchange (IKE) traffic and UDP port 1701 for L2TP traffic.

yes u have to open port manually port usually udp50
udp500 ipsec 50 udp 4500

You need to find out what port the VPN is running on. It could be anything. However, common VPN ports are not blocked normally and your problem is likely something else than a port issue.

My dns wasnt resolving over the vpn

Check on the Transport tab of the cisco vpn client setup (under modify).
I checked "Enable Transparent tunneling" using port 80 as well as "Allow Local Lan access"

to clarify, its protocol 47 that GRE uses, not port 47