Pregnancy vitamins?

Jessie
With my first she was a surprise so I didn't take pre natal vitamins but once I found out I took all the right ones. 
I'm now ttc and just wondering how important it actually is to start taking them before you fall pregnant? I'm overseas and it's hard to find good brands over here but I'll be home 2 weeks before Christmas. Will that be too late to start taking them or should I go on a shopping spree to try and find them?