Probably this is not a popular opinion but I'd go for Jira. Atlassian offers it for a very low price (10 USD / year I think) for small teams with up to 10 users. You can also self-host it if you do not want to store your data in the cloud, which for me is a large plus. It offers a lot of functionality but doesn't force you to use all of it, and it provides burndown charts and estimation features out of the box (https://www.atlassian.com/agile/tutorials/burndown-charts).
That said you could also use Gitlab, which keeps adding more functionality to their issue management. Trello might be a choice as well as there are plugins / third-party services available that can provide estimates, personally I'd not use it for software development though as I think it's not the right tool for this.