两者都有“获得”的意思：
gain 是普通用词，用法与 acquire 相似，常接抽象名词作其宾语，但不如
acquire 正式。 gain 可接
双宾语，相当于 win、earn 的用法。
1) I am new in the job but I am already gaining some experience.
虽然这项工作我是新手，但我已经在获得一些经验。
2）Don't go back to your old eating habits, or you'll gain all that weight
again.
别又恢复以前的饮食习惯，不然你又会变成跟以前一样胖。
3）It is imperative for a graduate to learn from the beginning to gain some
practical skills.
对于一个毕业生来说，从头学开始学习获得一些实际技能很重要。
4) His accomplishments have gained / won / earn him a reputation as a brilliant
expert in the subject.
他在这门学科取得的成就使他赢得杰出专家的声誉。
reap 本意是“收割”庄稼，可引申出“收获”，即“获得”的意思。
1) During past technological revolutions few of the companies that pioneered the
change proved to be good long-term investments, though some reaped the
financial rewards.
在过去的科技革新中，没有几家率先进行技术革新公司证明是理想的长期投资者，尽管它
们中有一些获得了经济回报。
2) Cultivating a wide circle of friends may reap a handsome payback in their
careers.
拥有一个广泛的
朋友圈可在事业上获得一个丰厚的回报。