what is best hacks for e-commerce growth ?

The best hack for e-commerce growth is

Tracking and analysing data is a great way to find and fix potential e-commerce growth bottlenecks.For example, you can use the following formulas to identify if your conversion rates are too low:
Conversion rate (%) = orders sold / visitors
or
Conversion rate (%) = orders sold / visits
If your conversion rates are below 2%, you might need to increase your online traffic volume or optimize your product pages. Here are some other ways you could do that:

Set up a Facebook Ad campaign on the fundamental principle of “lead magnet” i.e offer a free download in exchange for e-mail address.