Community edition - SIEM

There is no free level of Google Secops similar to the Google Cloud Free Tier.  You can contact a sales person to see about a trial for Google SecOps SIEM and/or SOAR.  Another alternative is the Security Community does offer live virtual workshops.  Coming up is one on Search and Rules which includes a Capture The Flag event and these offer hands on activity.  See the Community Events page for more info there.