This really depends on your budget. Plastic bachi are the most affordable type, but it’s rigidity often makes the playing experience frustrating (especially as a newcomer)
If you can afford it, you won’t regret investing in a high end bachi (like a Pantera Bachi or Signature Bachi), as it glides across the strings like butter and makes the experience infinitely more enjoyable. If you aren’t able to make such an investment yet, I’d recommend checking out a Wooden Bachi, as they offer a bit more flexibility while at a relatively low price point.