I am currently using an ISA and am planning to start a Pension Savings Fund

I am a beginner in stock investing.. Currently, I am only putting Tiger S&P500 and Kodex Nasdaq100 into my ISA, but I am planning to start a Pension Savings Fund as well. People around me are saying that I should also invest in overseas ETFs in the Pension Savings Fund; should I just hold similar assets to my ISA?