I don't know if anyone noticed this, but when you are having fun hiting the npcs in town you also get souls with critical hits!! Just hit the npc for 2 or 3 minutes and you'll fill your soul bar!! :D
This is an old and wonderful trick. I have about 2-3k soul bottles stored for 'rainy days'. buff, set auto-attack, then go and watch tv. 30 minutes later, collect my reward.
Ofc it's not against the eula! I was just joking. You don't even need to waste time making a stupid macro. Just go and stand behind an npc (for max crit rate) then force attack like you do in pvp, and just don't stop attacking. Simple as that. Also buying like a billion Soul Ore, when you do, is also good...
Once I hit like 4-5k, maybe 6k bottles I'll probably start using them even for normal leveling. The damage increase is fairly significant and at that point, I just don't care anymore. Especially when I can one-shot stuff with a nuke or Shining Edge (it's not 'that' weak. Even on a female SB with 2 less str. Fail more...)