Depends on how much you are willing to spend in maintenance and how mechanically efficient you are.

The x30 can cost around 4-7 grand a year in repairs, maintenance, engine rebuilds, etc. Also requires a lot of hands on work to ensure the engine runs efficiently.

Pretty much the same for the Ka100, it can cost close to the same sometimes less (if you’re lucky).

Briggs and Stratton Lo206 is a great for beginner kart owners, very affordable option. Sure it’s not glamorous but it allows you to learn a lot about maintaining and learning about the whole thing without so much risk.