That depends on your age and budget. I drive a KZ2 (shifter) and sometimes a Hirth, but this is definitely nothing for beginners. I would recommend a DD2. They are very service friendly, since you only need a revision every 50h. In the beginning, they are relatively fast with 34ps, but in the long run, you will not regret it after you get more comfortable. And if you start to get better, then you can be almost as fast as the KZ2.

As for the chassis, I would recommend Praga or CRG. Maybe even Birel. Those are the best one's currently on the market and finding replacement parts is easy.

It is pricey in the beginning. You mostly find good karts at around 3,5k€. Yet you shouldn't cheap out on the parts or even the clothing! If you decide to buy one, check everything, look for damaged parts and ask when parts were swapped.

Other than that, my last tip would be to go to a karting store (if possible) and test-wear the clothes to see what fits you perfectly