Migration of SharePoint 2010 on-premise to sharepoint online

Dear All,

We have only one web application with around 200 site collections (no customized webparts) and planning to migrate from SP2010 on-premise platform to SharePoint online. can you suggest me the steps to perform this migration without using any tools? or if we need to go with any third party tools which one is providing good service with low cost?

Besides, we have InfoPath forms and default approval workflows implemented in many site collections.

Thanks,

Vanathy