20 y/o making $3k/month, low expenses, best way to invest $1.5k/month for 4–5 years?

I’m 20 years old and make about $3,000 a month after tax, with very low expenses (around $400/month), so I’m able to invest roughly $1,500 each month.

I also have about $9,000 in cash right now. My time horizon is around 4–5 years, and while I want growth, I don’t want to take unnecessary or reckless risk. I may travel in the future, so liquidity matters in case of unexpected expenses. I’m not interested in day trading or meme stocks, I’m looking for a simple, long-term approach. Right now I’m considering broad index funds like VTI and keeping some money in a HYSA, but I’m unsure how aggressive I should be at my age and whether Bitcoin makes sense at all for a shorter timeline.

How would you allocate the $9k I already have, and would you go mostly stocks or keep more cash in my situation?