Noob question...

[En Passant]

I have just started to invest in Jan. of this year. I have about 5k in VTI (VANGUARD TOTAL STOCK MARKET ETF). With the market dropping a few points this week, I am looking to spend another 3k.

My question is, would it be wise to invest in a Vanguard mutual fund, or in a small cap that I feel is currently undervalued?

Also, what are the investments that you currently like?

Edit: I should also add, I am not scared of risky investments. I am young and it wouldn't be the end of the world if I lost 100% of my investments.