at one's own expense means to bear the expenses by oneself.
participating in the competition can exercise innovative thinking and improve professional ability. Improve the ability of teamwork. Improve language expression ability. Winning a prize can add a lot of color to your resume. Postgraduate entrance examination and retest plus points. Exercise PPT production level and improve the level of using office software. Get in touch with big bosses and broaden your horizons. During the competition, you may apply for patents and publish papers. The winner may get a bonus.