Synapse workspace cost reduction

I have a Cosmos DB where I have one container that contains different documents. One document is a main document that has another related document. Both documents are related to each other by using a partition key. There will be one main document and multiple event documents with the same partition key.

The main document has fields like date, country, and categories, which the event document does not have, while the event document has fields like event type, event dateandtime etc. To filter how many events happened for a particular category on a particular day, we have to use the main document. The events can be repetitive on a single day.

My requirement is to create a Power BI report to display how many events happened on a particular day and for which country in the last 2 months (each event should display only one time per category, per country in a day). I want to get this data from Synapse and load it into Power BI for the last 2 months. I used the Synapse view and implemented incremental dataset refresh in a power BI. In a Synapse view, I created a main view that loads data for a main document, and in another view, I get those partition keys from the main view and then load the data for an event document.

There are 2 dates in a main document: created date and change date. I cannot use the change date in incremental dataset refresh as it creates duplicate records, so I used the created date and then used the data to detect changes for the last 30 days (this is the time period where the main document can change). It works well, but the problem here is that it takes a lot of time to execute the query, which is causing more cost for data processing in Synapse.

Is there any suggestion to reduce the cost consumption of Synapse as well as query execution time/dataset refresh time in Power BI?