We have our data warehouse with AWS, and we are writing the queries to get the info that we need. We use Amazon Quicksight to analyze the data. We just started using it as it came out recently.
We have used MailChimp and SendGrid in the past. We are currently testing Appboy; we are integrating it right now. It is the new up-and-coming tool to acquire customers and gain attribution: an all-in-one email marketing tool. We have not completed the transition yet, but it works very well for analytics and notifications.
QuickBooks is a great tool to start out with. It holds up pretty well: I used to work at Kayak and we only had to switch away from it when our revenues passed $200M. QuickBooks Online is very simple--it integrates with taxes, and you do not have to be an accountant to manage it. It helps with paying bills and keeping track of your bank account; it also integrates with the Intuit Payroll system. You can get started with it very quickly.
Initially, we were just using Google Sheets but our needs grew. We tried a bunch of project management tools, and we settled on TargetProcess. It is a tool that creates agile/scrum processes. It mimics our development life cycle of two week sprints.