What percentage of my pay or savings should I allocate for investments?

After setting aside your emergency fund, you should be looking to invest a minimum of 20% of whatever you earn. If you're single with no commitments, try 60%.

Also, Unit Trust is just a tool, it's not an asset class. So make sure you're familiar with what you're invested in. A globally diversified portfolio that matches your risk profile via proper asset allocation is the key here.