The best way to better humanity is to better yourself.

可能極少人知 better 可以當 verb 來用
The best way to BETTER humanity is to BETTER yourself.
呢句兩個 better 同樣系 verb

better 當 verb 來用系解:
來自 Yahoo! 字典
1. 改善;改進;提高
He had tried hard to better his status, but failed.
他努力設法改善自己的地位,但未能成功。

way 來自 Yahoo! 字典
4. 方法,方式[C][(+to-v)]
Scientists are trying to find ways to prevent disease.
科學家們正試圖找到預防疾病的方法。

humanity 來自 Yahoo! 字典
2. (總稱)人;人類[J]
Humanity has made great progress in space exploration and medicine.
人類在太空研究和醫學上取得了很大進展。

Better yourself 來自 Oxford
To improve your social position through education, a better job, etc.:
Thousands of Victorian workers joined educational associations in an attempt to better themselves.

improve 來自 Yahoo! 字典
1. 改進,改善;增進
He put forward a plan for improving the rate of production.
他提出了一個提高生產率的計劃。

social 來自 Yahoo! 字典
1. 社會的;社會上的
Opinions on various social questions differ from person to person.
有關各種社會問題的意見因人而異。

position 來自 Yahoo! 字典
4. 地位,身分;位次[C][(+in)]
He has a high position in society.
他社會地位很高。

education 來自 Yahoo! 字典
1. 教育;培養;訓練[U][C][S1]
The government's policy on higher education is a success.
政府的高等教育政策很成功。

to better (verb) humanity = 改善 (verb) 人類
但中文甘寫會較好: 令 (verb) 人類 (noun) 進步 (adj.)

令人類進步最有效的方法就是改善自己(透過教育和較好的工作提高自己的社會地位)。

2007-01-26 16:33:22 補充：
best 系形容 way, 唔系形容 humanity

令人類改善0既最好方法係先令自己進步

最好的人類的最好的方法是對你自己更好 ~