Raw Broadsword+3
Undead Settlement
Light the Undead Settlement bonfire and head into the nearby dwelling to grab the Small Leather Shield. The shield is useful for parrying various bosses. Make your way to the Evangelist who kneels in front of a pyre. An Estus Shard is found between the Evangelist and the pyre. Titanite Shard x 6 are found at the Undead Settlement, allowing you to upgrade the Raw Broadsword to +3.
Rescue Cornyx of the Great Swamp, Dark Souls III
Rescue Cornyx, a merchant for pyromancy from whom you will purchase Poison Mist. Exhaust his dialogue, agree to learn pyromancy from him, and he would relocate to Firelink Shrine. Talk to Cornyx at Firelink Shrine to receive the Pyromancy Flame, a catalyst that allows you to cast various pyromancies.
Loretta's Bone, Estus Shard, Titanite Shard x 2 at Undead Settlement, Dark Souls III
Advance Greirat's quest line. Grab Loretta's Bone and give it to Greirat. Exhaust his dialogue, warp back to Firelink Shrine, and he should be in the curl up position. Warp to Firelink Shrine again, talk to him, and agree to send him on his first pillage quest. Now warp to Firelink Shrine again and he should have left the Shrine. Greirat will return to the Shrine again after you have defeated any area boss.
Make your way to the Road of Sacrifices bonfire and light it. Defeat the nearby Outrider Knight to obtain the Irithyll Straight Sword. This weapon is effective against the Dragonslayer Armour, a late-game boss. However, you can't properly wield the weapon until you have collected a ring found after defeating the boss, meaning that you can't use the weapon against the Dragonslayer Armour during your first SL1 run. Once you are able to properly one-hand the weapon, it has a move set identical to a straight sword but with a reach longer than the Broadsword.
Make peace with the giant archer. Collect a Young White Branch from him to allow you immunity against his arrows. Always have this particular branch in your inventory and don't move it to storage.
SL1 Cheese the Fire Demon at Undead Settlement, Dark Souls III
Initiate Siegward's quest line by helping him to defeat the Fire Demon. Ensure Siegward survives the fight. You need to follow Siegward's quest line in order for him to gift you a Titanite Slab. Defeating the Fire Demon would reward you with a Fire Gem, useful for infusing the Dagger to give you high damage output from backstab and riposte.
Titanite Shard x 2 & Undead Bone Shard at Undead Settlement, Dark Souls III
SL1 How to cheese Hodrick, Dark Souls III
Proceed to the Dilapidated Bridge bonfire and light it. As you make your way to the birch tree, Hodrick would invade you. Lure him to the birch tree and jump to the platform containing an Undead Bone Shard. Stand near the Undead Bone Shard, wait for the giant archer to kill all enemies wandering the area, and for Hodrick to fall off the edge. Collect all Young White Branches near the birch tree to advance the quest line of the giant archer.
Pick up the Caestus near the Dilapidated Bridge bonfire. In a later area, you will collect a Blessed Gem, which can be used to infuse the Caestus and give you HP regeneration. Until the Caestus can be infused with a Blessed Gem, you should collect the Blessed Red and White Shield+1 to give you some HP regeneration. The Caestus also functions as a weapon for reaction parry, useful against various bosses. The Small Leather Shield is another useful weapon for parrying various bosses. If for some reason you are unable to use the Blessed Caestus to parry, e.g. you're using the effect of the Red Tearstone Ring and don't want HP regeneration, consider using the Small Leather Shield.
Location of Mortician's Ashes, Dark Souls III
Titanite Shard x 2 & Blessed Red and White Shield+1 at Undead Settlement, Dark Souls III
Rescue Irina of Carim, Dark Souls III
Grab the Mortician's Ashes, give it to the Shrine Handmaid, and purchase the Grave Key for 1,500 souls. You need this key to open a locked door near the Dilapidated Bridge bonfire. The door leads to an area containing Titanite Shard x 2, the Blessed Red and White Shield+1, and Irina. Locate Irina, exhaust her dialogue, accept her services, and she should relocate to Firelink Shrine. You need to follow her quest line to purchase Tears of Denial from her, among other miracles. Following Irina's quest line would also allow you to summon Eygon at the Crucifixion Woods (before the fog wall of Crystal Sage) and at Lothric Castle (before the fog wall of Dragonslayer Armour). Summon Eygon to help you clear an area and allow you to safely grab treasures.
Locations of Flynn's Ring & Chloranthy Ring, Dark Souls III
Two useful rings found at the Undead Settlement are Flynn's Ring and the Chloranthy Ring. With Flynn's Ring equipped, lowering your Equip Load would boost your damage output. The lower is your Equip Load, the higher is the damage boost. The Chloranthy Ring boosts your stamina regeneration by seven points per second. At a later area, you will grab the Grass Crest Shield, which further boosts your stamina regeneration. The effect of the Grass Crest Shield stacks with the effect of the Chloranthy Ring.