One approach is to use ETFs. I'm assuming you'll want 20% international:
80% VTI = Vanguard Total Stock Market ETF
20% VXUS = Vanguard Total International ETF
You could also go with admiral class shares, which have a new minimum of $3,000 (down from $10,000 minimum):
70% VTSAX = Vanguard Total Stock Market, admiral shares
30% VTIAX = Vanguard Total International, admiral shares ($3,000 meets the minimum)
If you prefer mutual funds but want less than 30%, I think Vanguard has closed the investor class versions of their international funds. So I'm not sure what fund you'd select in that case.