I thought I would quickly gather some of the resources available to you now and at no cost for you to increase your knowledge of Atlassian products.
Atlassian offers free introductory level training great for new users and free skill-builders intended for those with or want to have Administrator permissions. Check out their free training catalogue.
If you are thinking at an organisation level, check out the Training for Jira app which also includes a progress report view for Administrators.
Why should I consider Atlassian training and how so I decide what is right for me?
Check out this three-part series written last year (by me). They are mostly still accurate.
As of 11 December 2019, a lot of the numbers in this article became out of date due to the fantastic improvements to the Atlassian Certification program outlined here. An updated version of Maintaining your certifications in 2020 is here.
Other free training