我不太懂股票，所以不敢随便投机。

Wǒ bú tài dǒng gǔpiào, suǒyǐ bù gǎn suíbiàn tóujī.

I don’t really understand stocks, so I don’t dare to speculate casually.

他靠炒房投机赚了很多钱。

Tā kào chǎofáng tóujī zhuàn le hěn duō qián.

He made a lot of money by speculating in real estate.