Best place to farm Enthu is the Burning Temple (Druid). It's because breaking the ring is pretty easy with 2 well placed spears. That will increase the drop core to +1. If you pop vip and get guild +1 extra core with pet with +1 extra core, you can farm that area pretty well, especially if you have multiple characters.
Once that area is farmed, you can do Gates of Hell (Lavasat). If you're desperate, do Lako as well (if you're 95 and above, Lako cost money to run).