Editing posts is definitely a way of earning reputation, but it's not the most efficient. The nominal 2 reputation you receive per accepted suggested edit won't earn you a great deal of reputation unless you edit a lot.
My Stack Overflow profile mainly consists of editing posts. At the time of writing, I have over 400 approved suggested edits, earning me 748 reputation out of a total ~1100. However, these 400 edits took a large proportion of time compared with the 13 answers I've provided, earning me ~300 reputation. Those 13 answers didn't take very long to write and the reward for the effort I gave was worth it far more than the suggested edits.
In a more extreme case, here on Ask Different, I've earned 160 reputation from my lifetime of suggested edits, including tag wiki edits—an insignificant contribution to the ~35k reputation from other means.
Only when you edit many, many edits very quickly do they become a worthwhile strategy for earning reputation, but suggested edits should be substantial improvements to a post and making minor/bad edits would get you suspended if they get rejected.
Posting great answers will earn you plenty of reputation, far exceeding that from suggested edits.
Finally, a point of note regarding rejected suggested edits: yes, there's no penalty for having a few rejected edits, but having a high reject/approve ratio will get you suspended, if not manually by a moderator.