What is there that makes a workflow suitable for automation in a small development team?

I'm considering the possibility of small development teams spending less time on repetitive tasks and more time on solving actual problems.

For instance, a team could end up spending hours each week on manual testing, carrying out deployment checks, preparing bug reports, or keeping the project updates in order. However, it isn't always the case that everything should be automated since the costs involved in setting it up and in maintaining it can end up exceeding the time that is saved.

I would like to get some feedback from developers and startup teams who have dealt with this issue.

What is the basis on which you choose the first repetitive task to automate and was the outcome worth the trouble?

I should particularly like to see examples of what succeeded, what failed, and the reasons for this.