Is doing just on cumulative update a month ok??

abacus said:

Is there any reason that I should install all cumulative updates within one month? As long as the Patch Tuesday one is installed, isn't that enough??

That question is asked a lot. Right now, with the preparation for the October new release, there are more and more frequent updates. Tying up loose ends in prep for the release. This MS article explains a lot about how/what/why they do with updates. Take a look. It may answer some of your questions.

Windows 10 update servicing cadence - Windows 10 Forums

abacus said:

Is there any reason that I should install all cumulative updates within one month? As long as the Patch Tuesday one is installed, isn't that enough??

For security purposes, the Patch Tuesday one is the only one you need. The others are just quality updates and bug fixes.

Microsoft said:

Update Tuesday (most often referred to as Patch Tuesday) updates are ... the only regular releases that include new security fixes.

Windows 10 update servicing cadence - Windows 10 Forums

Except for Hot-fixes and emergency patches. They can come any time. That's the same link I posted.