The X30 would be a good bet right now. For 125cc TaG engines, it’s probably one of the more reliable ones, nice to drive, and it’s popular around the country so parts would be easy to get.
If you’re looking for something in between Yamaha and 125cc, you might want to look at the KA100 engine which is rapidly gaining popularity right now. Easy to use air-cooled 100cc, like a Yamaha, but far more reliable and has an on-board starter so it’s easy to go solo on practice days. And it’s great to drive.