How should a uni grad start investing $20k if I have cleared my student loan debt?

For a start maybe go through robo advisor since you are new, no need to fomo and rush into it. Learn first, then slowly move over to DIY next time onceyou gain knowledge and have capital. For now, focus on clearing your student loan and set aside emergency funds.

Start now and dollar cost average. Many people will tell you to go into index funds, ETFs or use Robo investors. Don’t. Spend the time researching and learning how to invest on your own. There is a satisfaction of proving your thesis right AND earning returns. E.g I was long on AMD at 11, and now they are at 98 because I saw the potential in their CEO and business.

You are young and what you have is time. Time means you can invest in riskier bets and stomach volatility. Why go with 10% per year when you have the runway for 1000%? Just another POV.