First, the research.
Shortly after being assigned to Rakuten's onboarding and acquisition team, I spent my first few weeks understanding customer insights and researching our platform metrics. Based on metrics alone, I was able to discover a major drop-off in "one-and-done" users; that is, people that signed up and never returned. After investigation, it was clear that users were experiencing confusion, skepticism, and apathy due to low incentives for making their first purchase after signing up. 
Next, the level of effort
With a deeper understanding of our friction points, there were many directions we could have taken. I got engineering involved early to investigate the LOEs for our most promising solutions. 
Third, the pitch
I synthesized my research findings, the engineering LOE document, and qualitative + quantitative feedback from our users and created a pitch deck for the CEO and executive leadership outlining a 7-step plan to get us back on track by end of year. (Click the slides below to advance).
Success!
The CEO and executive team gave us the green light to move forward. The next step was mapping out our plan of attack, to include current phase and impact / effort scales for each of the 7 initiatives.
So... should we build all of it?
Knowing that our end-of-year code freeze was approaching just a few months away, we chose the initiatives we felt had the most impact with reasonable effort to build, test, and deploy. We decided to pursue incentivized milestones and offering a percent reward instead of a dollar reward. 
Test Time
We wanted to know if there would be any interest in offering a percentage-based reward instead of a fixed dollar amount. I threw together a quick AB test to compare % vs $ cash back incentives, and tested 40 users; half of which had recently signed up, and the other half who had recently used our competitors. Of each 20, 10 received Variant A (which showcased a dollar amount first) and the other half received Variant B (which showcased a percent back first). Here was a highlight reel of our findings:
Results
Even though we were able to generate interest in our percent back theory, we discovered that the order in which we displayed the rewards had a higher impact than the rewards themselves, so we opted not to move forward with this initiative.
What else might we build?
The $ vs % cash back initiative didn't prove fruitful, but we did find success with three other projects. Specifically, incentivizing onboarding milestones, letting users choose favorite stores after signup, and letting visitors "test drive" Rakuten before being forced to sign up. I ran a quick, Crazy 8 Session with my product and design partners to quickly ideate solutions before refining each solution.
Solution 1: Incentivized Milestones
This solution focused on incentivizing new users to complete the three critical steps required to get their first paycheck; signing up, adding their payment credentials, and making a qualifying purchase. Since we were already offering a welcome bonus, why not break the bonus into three steps that both educate and incentivize users to complete onboarding?
Solution 2: Collecting Explicit Signals (Store Favorites)
We knew very little about anonymous users signing up to our platform which made presenting relevant content to them extremely difficult. By allowing users to select a few of their favorite stores after signing up, we were able to curate a more valuable home feed which immediately increased engagement and first-time purchase conversion. 
Solution 3: Visitor Test Drive
For our mobile web users, there was no way to explore Rakuten's offerings without first signing up. By allowing anonymous visitors to "test drive" our home feed, we hoped to lower skepticism, demonstrate our value, and improve both the quality and quantity of our signups. However, we didn't want to throw them into the world's largest Costco without a map. Instead, we leveraged our current home feed with customized header banners, a social proof section, a curated section of our most popular stores, and a sticky footer to communicate our signup bonus. 
Results
All three onboarding initiatives were researched, pitched, designed, and handed off within 12 weeks. Each initiative is being AB tested and though the test results aren't officially synthesized yet, early signs are showing a huge success in converting new users to paid shoppers, with an estimated revenue boost of $8.25M this year
Stakeholders    Rakuten Senior Executives and CEO
Engineering Lead    Vinh Huynh
Product Manager    Michael Arioto
Product Design, IA, UX, UI    James Lacey
UX Writer    Carolyn Twomey
User Testing / Research    James Lacey, Daniela Governatori
Final Prototypes and Design to Dev Handoff    James Lacey