Non-US citizen, Where should I invest in ETFs similar to VOO and VXUS? confused..

Hi, i live in southeast asia/middle east, 30 year olds (i know im late) and I'm wondering if its okay to start only with VOO + VXUS? Over here we don't have 401K/roth (though i am still confused what they are) and also there is 0% taxes in our salary and i will be graduating from medical school this year so i want to start right away through residency and I read that the two i mentioned have around 30% taxes if i am a US citizen so Im not sure on which to start investing in.