Make portfolio viewing more attractive
Although koinly is currently the best in terms of API tracking and integration, it's not the most aesthetically pleasing for looking at your portfolio. For me in terms of aesthetically pleasing, coin market cap is definitely the gold standard. Coin gecko and coin stats are right behind it. But koinly is way behind in this area.
If you really want to be great, I would suggest creating a tab for looking at the portfolio that has really nice line graphs, pie charts, etc.
People want to be able to view their portfolio on mobile on a regular basis, and just get a clear update of their gains and losses for the day, and so on.