Things to look for before buying project management tool

Hi everyone, I’m handling a marketing team of 5 members in a startup. I’m looking for a project management tool that helps in task management and improves my team’s productivity. Can anyone suggest a good tool for the same? What tools you people are currently using?
What are the things to be checked before buying one?

I have been using Basecamp for 15+ years and it is easy for my clients to follow along without training.