dark woods/ black marsh, then head into tower at around level 6
Do tower til 12
far oasis beetles and arcane til 15 (or other areas with beetles in act 2)
Start clearing tombs til 20
20-24 cows
25 ancients/norm baal

If you are still solo, nm cows will be your next fast xp - get chanted and 3 nm cow clears will get you 40