General well-wishes:
* 祝你一切顺利 (zhù nǐ yīqiè shùnlì): This literally translates to "wish you all the best" and is a very common way to express well wishes.
* 祝你好运 (zhù nǐ hǎo yùn): This means "good luck to you" and is a more casual way to express well wishes.
* 保重 (bǎozhòng): This means "take care" and is often used as a way to wish someone well, particularly when they are leaving.
More specific blessings:
* 愿你平安 (yuàn nǐ píng'ān): This means "may you be safe" and is a good way to express a wish for someone's well-being.
* 愿你幸福 (yuàn nǐ xìngfú): This means "may you be happy" and is a way to express a wish for someone's happiness.
If you're specifically referring to a religious context, you could use:
* 上帝保佑 (shàngdì bǎoyòu): This literally means "God bless" and is a direct translation of the phrase. However, it may not be appropriate in all contexts, as it is considered very religious.
Ultimately, the best way to express "God bless" in Mandarin will depend on the specific context and the person you are talking to.