How to update/patch the host not only depends on the missing patches, but also on whether it has been installed using a hardware vendor customized ESXi image. In such a case you may also need to update the venor's drivers and tools. You may also consider to update the hosts' firmware to have your hosts in a supported state.
Last but not least, think about updating vCenter Server, and any related applications (e.g. backup), so that everything continues to works together after the update.
When you apply updates to a host it will automatically select the updates that are needed. And will also apply them in the correct order. So you only need to start the update and wait...