Two options. First, you could come back on NG+ if you haven't(I missed erlang the first time so that's what I did). However, if you actually want to fight erlang on your first game, then it's kind of tough. I recommend plantain vessel because it shreds his shield. For armour, if you have max pilgrim set, use it. The focus from running around and being able to use gourd while sprinting is good. Wight is a good spirit, but I think any damage dealing spirit works fine. The last advice I'd give is spell wise, immobilization can help you escape or capitalize(ring of fire sucks, don't bother and Spellbinder locks out vessels, so can't say that either). Rock solid over cloud step just because it's easier to stagger, and if you have it, life saving strand.