My advice would be either the Varrock sewer resource dungeon (65 dungeoneering) or the Gnome Stronghold. For a bot, i would use ArteChop or Lumberjack.
From my experience, I would say as long as you have a dependable bot just do it near mage tower in camealot. For example, I got the premium auth from rsbots.net and I was able to bot 24 hours+ with that auth bot. My old account still has 22M woodcutting xp from botting mages at mage tower.