Metrics and Logging tools.

Hi All, We are building a B2C product and anticipating 2.5lac DAU. Shall be starting with a small team of 10 engineers. Could some one suggest a cheapest tool that will have 1. Metrics 2. Logging 3. Correlation of the above 2. So preferably both of them in one place. I have used datadog in the past and really liked it but it is out of our budget for now. I am thinking of using ELK with Prometheus though system metrics and logs will be separated. And with aws cloud watch, cost is a concern and do not want engineers to look at AWS dashboard for all debugging and monitoring purpose. ( We might also use Azure or GCP later, if we get startup credits. So then separate tools for logging might be an overhead. Anyone from past experience, any suggestions?