I'm 23 and have set aside $20K to begin investing. Where do I begin and how should I diversify?

I would suggest the Roboadviser route if you have zero experience.

Stashaway or Syfe are good options.

Ask yourself these four questions.

1. Do you have sufficient coverage insurance before starting investing?

2. Do you have at least 6 months worth of expenses as emergency funds?

3. Do you have recurring income while investing?

4. Do you foresee that you have any big ticket purchases in the near future?

One is only ready for investment if these four considerations are met. As a beginner, I have been advising the use of passive investing. Which means you can either start off with robo advisors or ETF RSP like FSMOne.