I am assuming that it's for your personal project. If yes, there are many free tools available - both open-source and commercial. Most of the commercial tools provide their tools/libraries for free for personal use.
Here are some pointers:
If you want a more robust comparison: try this tabular comparison of JavaScript charting libraries.
I can point to more specific tools/libraries as well, if you can let me know if you are looking for tools that require coding or not.
Hope this helps!
Well you have 3 main components:
the data the visual representation of data the management of your representation
I would build an Angular app, create a view for the dashboard and feed my view with data fetched from the google sheet. I don't now much about Supermetrics, but I would just build the graphs using something like Fusion Charts. http://www.fusioncharts.com/angularjs-charts/#/demos/ex1. You can feed Fusion Charts data using the Google Sheets REST API.
As for editing the data view, Angular lets you write snippits of code and use a controller to call those snippits dynamically. The controller can build a default view, but hitting the edit button could allow people to drag and drop your dashboard widgets or add new ones from a list.
I think the Fusion Charts Pricing Page is what confuses me. The only place where it says you can use it in SaaS requires you to fill out a contact form, which tells me the price must be kind-of high.
According to your link, I can pay $390 at minimum to use Highcharts in the same way. Plus Fusion Charts kinda look like they were made in Excel 2003 and don't appear to have smooth animation.
How about something like a pie chart you can move the parts by pulling them.
I've used Fusion Charts Free for a couple projects and it's worked well. Of course it's Flash, but honestly my clients don't care (in fact, they're happy that it's "flashy" lol).
http://www.jqplot.com/ http://www.fusioncharts.com/free/
I prefer jqplot, it's much easier to work with and doesn't use flash, but browser support on IE is not 100% certain. Also, there are no animations like in fusion charts, but I don't particularly care.
Spark Line, like jqplot, is easy to use and specializes in small in-line graphs.
As for generating data to feed to the charts, well that's an implementation detail