invest time in
invest (one's) time in (something)
To put forth effort toward some task or goal. If I invest my time in this project, I want to see some good returns.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
invest someone's time in something
Fig. to put one's time, effort, or energy into a project. Mary invests her time in charity work. I invested five weeks of my time building this model ship.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.