The cave is an alternate path to the boss in huntsman's copse, doesn't lead anywhere new, just access to a few items along the way.

I went to the wrong boss first in Huntsman's copse, defeated the charriot at undead crypt. That seems to be a dead end. Some dwarf wants to know if I have a taste for blood, I said no, and went to the other end. That boss was pretty hard, main targets easy, skeleton wave doable, spinning wheel wave impossible to dodge all and find time to sqeeze off a spell. With an ally it was fine.

I found a girl selling 10 titanite at the entrance of harvest valley. Not enough but together with what I found along the way at least my priest chime and robe are up to +6 now.

You can find a few titanite chunks in Black gulch. I thought I had enough to get sorcerer's staff to +9, but it's only +8, I still need 2 more chunks. I did get quite a few large titanite shards there. Maybe you have better luck with titanite chunk drops. It's pretty easy to farm the enemies there, once you get rid of the poison spewing statues they don't come back as long as you don't die and stay in the area. It's a relatively small area, quick to reset at the bonfire to try again for more drops.

It was one of the harder bosses for me, not as hard as the royal rat vanguard but that group of spinning wheels attacking from all directions ranks a close second. (Hated them in DS as well) I got the titanite, still hungry for more :) I bought a new staff, but no clue when it will become better than my current +8 one, or if I'll find an even better one later. There are so few resources to try things out.

Right now I am about 30 hours into Demon's Souls, and I am very addicted

Yeah later on i'm sure that you will have titanite chunk drops.

I'm currently in a woods area with unlockable/semi invisible enemies -.-. Just beat the area boss on my first try, incredibly easy especially with the messages of others. But aftert that i explored the area a little more before moving on and i had to spend 10k to repair my items god damn frogs. And sadly i killed an NPC, which looked exactly like a falcon from the Painted World. Though i found a merchant that sells the claymore as well as infiite Gold PIne Rasin and i got 13 of them. 

I suggest changing this thread title into Dark Souls II official thread

Just butchered those three bosses of The Lost Bastille all by myself, I feel like a bad-ass :P

I've gottent the ..... at risk message before. If I can't swap it out i run back to the bonfire to reset durability. Luckily nothing broken yet, except for the ring meant to break to save your souls. First time I tried that boss with the spinning wheels at the end I had 80k souls on me, good thing I used it.

I went through Harvest valley and Earthen peak last night. Kinda uninspiring levels, not upto Dark souls standards imo. They were merely ok, b-side material, including the bosses. Hopefully Iron keep will step it up again. Those areas did drop enough titanite to get my armor upto +3 and robe to +7, plus I also upgraded arch drake shield to +4 to use that now. I dropped out my secondary sword as I wasn't using it anyway, so I could carry a heavier shield and stay under 50% equipment load. Speed is basically my only short range defense.

I still got killed again, messages warning of ambushes are nice, but not being able to withstand more than 2 hits makes the first attempt usually a 'learning experience'. Plus a damn chest ate me, full health bar gone in 1 shot. That's when I had my first soul loss, 30K. On retrieval a spell missed and 2 fast moving dual wielding enemies close to the bonfire blocked the way and sliced me to pieces.

I have a bonfire aesthetic now. I'm wondering wether I should use it in black gulch to hopefully get more titinite chunks or keep it for somewhere else. I still need 2 more to get the socerer's staff to +9.

I think it's about 85 or so, but with Third Dragon Ring and Soldier Ring +1 (the one that increases your load), i'm at the 65% threshold. 

I'm using a Lightning Drangleic Sword +5 as my main weapon for now, but once I've got enough Petrified Dragon Bones, I'm gonna switch to the King's Ultra Greatsword (after elementalizing it to Lightning), so I might drop a few weight on the armor department.

I just beat the Gargoyles+ the Sinners rise boss. Used a branch in the lost bastille and i found a merchant that lets you trade boss souls for items(He also sells special spells). Got myself 3 nice weapons but i won't be using them yet, they have low bases but they scale so well with upgrades and i don't have enough dragon bones. 

As far as i know Earthen Peak has two bosses, i beat the first one and i'm omw to the second but casters are annoying after you run out of arrows. I would use the bonefire aesthetic in the tower of heide since it is by ar the funest area to me. You can buy one from the titanite merchant in the harvest valley. 

Why are you preffering lightning? You on NG+?

Yeah I found that merchant too. He had two spells for trade, the weapons are all useless to me. My str and dex are 15.
What are dragon bones for?

You're right the other boss was in Earthen peak too, not harvest valley. That was no contest, the arena was a bit small but the thing is so slow I had plenty of time to run turn cast, repeat. The casters later on are easy too as a caster, with a bit of blind targeting they never even fire off a shot. The dual wielding fast moving enemies were my undoing.  Tip for the 2nd boss: The fight is a lot easier if you turn off the poison factory first, but setting the large axle on fire with a torch, just outside of the upper bonfire.

Heide was indeed fun, but no real useful resources there. The bastille is still my favorite from the game so far.