Best place to farm herbs to heal is boletarian palace (world 1-1 then part 1 -3), What-ever-its-name-is-again mines is good for stones for upgrades (world 2-1, 2-2 where the crystal lyzard pit is).
Also if you want to farm for souls go to the shrine of storms and kill of the skeletons (they give about 300 to 500 souls each) they are weak to magical attacks, and yes you can leave a level and retain your souls to buy/ repair equipment.
Always run around with your shield up! (if you have a good shield.....) or always be ready to comabt roll out of the way (if you go this route wear light armour)
Worst comes to worst just try luring one enemy out at a time, or you can try getting the Large Sword Of Moonlight (faith based build needed or you do no damedge), thiss word ignores any and all shields.
Try getting fire based weaponry as alot of foes seam to be weak against fire.
I have to be a ass-hat on this point, im on new game ++ (beat the game twice with the same character, dificulty is 150% ontop of the orriginal stats of foes) so you have no idea what fury this game has to unleash.....yet

(i cant even continew as i botched my character build)
Stay focused with where you take your heros build! Eitehr stay melee, ranged (with some melee as it is dificult to pure range the game), mage, or faith build which meshes melee and holy spells to heal you (or do some insane damedge with Gods Wrath miracle)
What character did you start with? some are alot esier to start off with then others: Temple knight can be very difficult whereas the soldire or wanderer are more simple to get the hang of.
Just a thing to remember is The more heavy armour you wear the more you stamina drops (including when you attack) and the slower you combat roll, where if you wear lighter armour your stamina drops at a drasticaly slower rate (allowing for more attacsk, unless you use 2 handed weapons those just rape stamina nomater what you do) and you combat roll like an oiled rat down a water slide at a 90 degree angle.
Be carefull with some soul signs left by other players, they can often lead you to traps or areas were you are forced to die to continew.
And if you die, try getting back to where you jsut died as slowly and safely as you can, your souls will be there UNLESS YOU DIE AGAIN, then they are gone for good (ive lsot 100k souls at once, trust me it sucks when you even permanently loose 5k souls)
Sorry for the giant wall o text
TL,DR you missed alot of good pointers
Tazz