For beginners, I'd recommend Google Home or Alexa over Apple HomeKit. The reason: they're just cheaper to get started with and you'll find way more compatible devices for them. With Apple you often pay more and then you still need a HomePod mini as a hub, which means extra costs. Google Home and Alexa, on the other hand, have lots of cheap entry-level devices and work with most of the stuff you find in stores.
If you have to choose between Google and Alexa: Alexa (so Amazon) is probably a bit more beginner-friendly because the devices are cheaper and you can quickly get going with Echo Dots or whatever. Google Home is solid too, but Alexa just has the bigger selection of cheap smart plugs and lights. What they both have in common is that you can use them without a separate hub device - a smart speaker is plenty to start with.
For a small rental apartment you don't need anything fancy anyway. Just start with an Echo Dot or Google Home Mini, maybe add a smart bulb and a smart plug, and see if the system works for you. You can always expand later. I'd only go with HomeKit if you're planning to stick with the Apple ecosystem long-term - otherwise you're just asking for headaches.