There is no cap on the number of optimization changes that you can make in a specific time period in AdWords.
But try to avoid a lot of changes in a short span of time. Make optimization chanages based on statistically significant data. And after making the changes, measure the impact/result of those changes and make further changes based on that analysis.
Optimization will be meaningful only if you measure the results accurately and make changes accordingly. So from the beginning, remember to use tools like AdWords conversion tracking or Google Analytics goals to measure the performance of your campaigns.
Find more information about tools to measure your campaign performance here - https://support.google.com/partners/answer/6172662?hl=en&ref_topic=6123873
You can find some basic information about campaign optimization here - https://support.google.com/partners/answer/6172658?hl=en&ref_topic=6123873