If new car, then just follow the recommended service. I believe for Myvi, the suggested oil is actually Perodua oil made by Petronas and it's only mineral, not even semi-synth. So if you want to upgrade, semi-synth is more than enough already, and better to switch only by the 5000km oil change to allow the piston rings to settle properly first with the mineral oil.
The 0W30, 5W30, etc2. indicates the multi-viscosity rating of the oil. A 5W30 means the oil is rated to have a viscosity rating of 5 during cold (denoted by the W = winter) and would not get thinner than 30 viscosity rating during hot operating temperature. If you want to learn more, than this link is a good start: http://www.carbibles.com/engineoil_bible.html