That's awesome! I'll have to check out your app. I am a big advocate for a three-fund low-cost index approach(1) but I acknowledge that there can be specific circumstances per investor.
basically platformitizing great minds like Warren Buffet and Peter Lynch
May I also humbly suggest researching John Bogle, the founder of Vanguard? There is a very active investment community on https://www.bogleheads.org/forum
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(1) Vanguard S&P 500 Index Fund, Vanguard Total International Stock Index Fund and Vanguard Total Bond Market Index Fund. Those three funds give a diversified exposure to the entire market. Using Vanguard (or Fidelity) is a great way to lower costs as is using a simple three-fund portfolio. The thing to avoid is the approach that many high-fee money managers use to put someone into 12-15 funds that have high loads and then rebalance monthly while they're marking up the buys and marking down the sells. I had a coworker one time realize that he was paying high five figures in fees per year to a certain unnamed popular money manager through their hidden fees.