obtain,经常表示付出一段时间努力之后"获得"某些东西,譬如说advice, benefits, approval, a degree, information.

例句:teenagers have to obtain permission from parents before they go out with friends.(青少年需要获得父母的允许才能够和朋友出外.)

gain 强调获得的东西是对你有利或者有帮助的东西,譬如说the access to something, advantage, benefit, control, insight, knowledge, confidence, support, power等等

例句:impulse sometimes gains power over nature. (冲动有时候会战胜本性.)

acquire 强调通过购买或者强夺的手段去获得一些东西,这些东西一般是可见的,譬如说asset, company, status, title, property;

acquire 有时候和gain的意思差不多,可以加skill, knowledge, 但是acquire给人的感觉就是获得之后还会长时间占有, 所以我自己一般喜欢用acquire skills or knowledge.

例句:with thought, practice and feedback, we acquire skills. (有了思考,实践和反馈,我们可以获得技能.)