"Money buys a gun or two. Thrill buys a reputation."
Starting Items
Doran's Blade & 1 Health Potion
After patch 13.20 this is your default start against most lanes. The bonus HP from Doran's Blade is very useful in all-ins. The lifesteal also scales pretty well so hold this item as long as you can.
Long Sword & 3 Health Potions
Against heavy poke lanes you will need some extra sustain. Gives you a faster Serrated Dirk as well. Just keep in mind that you lack that extra 100 HP from Doran's Blade so you might wanna avoid early level all-ins.
First B / Early Buys
B.F. Sword
Getting a B. F. Sword on an early base can be difficult but make sure to grab it if you can. Builds into The Collector and Infinity Edge.
Serrated Dirk
Solid component that upgrades into The Collector, Hubris or Youmuu's Ghostblade.
Vampiric Scepter
Decent sustain item if you're planning to build Immortal Shieldbow as a first or a second item.
Pickaxe
Builds into both The Collector and Infinity Edge which are usually your first items.
Refillable Potion
If you have some extra gold and the game is still in early laning phase (before 10min).
Boots
Grab tier 1 boots if you don't have any damage items to buy or if you need to get back to the lane faster.
First Item
The Collector
Simply the most reliable first item for Samira.
Infinity Edge
A very expensive but also a very strong item. Usually you would be buying The Collector first but if you just have the money grabbing IE is a good idea since it just gives an insane amount of AD.
Immortal Shieldbow
Decent item that provides both sustain and survivability. Just make sure to grab a Serrated Dirk before this so you won't lack damage.
Hubris
Extremely fun snowballing item for fistfight games, just keep in mind that you shouldn't buy it on autopilot every single game.
Youmuu's Ghostblade
The stats are almost equal to The Collector and it's 500 gold cheaper, grab this for tempo if you don't have the money for The Collector yet.
Second Item
Infinity Edge
If you rushed The Collector you usually want this after it.
The Collector
Default second item if you didn't buy it first.
Immortal Shieldbow
If the enemy team has many assassins or a lot of poke you might need some safety or sustain. Excellent synergy with Last Stand.
Youmuu's Ghostblade
If you already have The Collector, enemy team is squishy and you just have the money for it. Good cheap item for tempo.
Hubris
Extremely fun snowballing item for fistfight games, just keep in mind that you shouldn't buy it on autopilot every single game.
Profane Hydra
You already have good waveclear so this item is not for that, it just gives you really strong damage in combos and all-ins. You can and you should use the active during your Blade Whirl or Inferno Trigger.
Third Item
Infinity Edge
If your first 2 items were The Collector and Immortal Shieldbow, BUY THIS RIGHT NOW!
Lord Dominik's Regards
About 70% of the time this is your best third item. This is when people are starting to have enough bonus armor for it to have proper value.
Immortal Shieldbow
If the enemy team has many assassins or a lot of poke you might need some safety or sustain. Excellent synergy with Last Stand.
Bloodthirster
If the enemy team has a lot of poke and you really need some sustain this is very useful.
The Collector
A fine item to close out games against squishy teamcomps.
Mortal Reminder
Before the changes in patch 13.1B this item used to be completely useless on Samira, however with the attack speed removed and armor pen added it is now very good in certain situations. If you are facing many healing champs and your team isn't building any healing reduction this item is highly recommended.
Maw of Malmortius
If the enemy team is AP heavy and you didn't buy Immortal Shieldbow this is your best defensive item.
Opportunity
Just like Youmuu's Ghostblade, a good cheap item for tempo against squishy teamcomps.
Hubris
This is still good as a third item, I wouldn't buy it any later than this.
Profane Hydra
You already have good waveclear so this item is not for that, it just gives you really strong damage in combos and all-ins. You can and you should use the active during your Blade Whirl or Inferno Trigger.
Fourth Item
Lord Dominik's Regards
If you still didn't buy any armor pen and the enemy team is getting tankier, now is the time to do so.
Mortal Reminder
Before the changes in patch 13.1B this item used to be completely useless on Samira, however with the attack speed removed and armor pen added it is now very good in certain situations. If you are facing many healing champs and your team isn't building any healing reduction this item is highly recommended.
Bloodthirster
At this stage of the game Bloodthirster always works if you don't have any other situational items to buy.
Death's Dance
Really good defensive item that also gives you some damage. Helps you carry teamfights, even better against AD heavy teams.
Mercurial Scimitar
If you are playing against uncleansable CC ( Malzahar, Skarner).
Jak'Sho, The Protean
Solid item for long teamfights where you just wanna stay alive to do damage.
Serylda's Grudge
A fun off-meta armor pen option. Makes your Inferno Trigger harder to escape.
Black Cleaver
Excellent armor pen choice against 2+ heavy armor champs, really fast to stack on Samira since it requires 6 attacks (just like S-tier), also great if your team is AD heavy since it shreds the armor for others too.
Frozen Heart
A very cheap armor item against heavy AD comps.
Opportunity
Just like Youmuu's Ghostblade, a good cheap item for tempo against squishy teamcomps.
Last Item
Guardian Angel
Really good defensive item against assassin-heavy comps. If you went Ingenious Hunter always buy GA as a last item since the cooldown is extremely low.
Bloodthirster
This item is stronger the later you buy it, very strong at level 18.
Death's Dance
Really good defensive item that also gives you some damage. Helps you carry teamfights, even better against AD heavy teams.
Kaenic Rookern
Extremely strong item against AP heavy comps.
Spirit Visage
Another strong item against AP, even better if you have an enchanter. It also improves your Immortal Shieldbow shield and all your lifesteal.
Randuin's Omen
Great choice against 2+ crit champs ( Yasuo / Yone + crit ADC).
Black Cleaver
Excellent armor pen choice against 2+ heavy armor champs, really fast to stack on Samira since it requires 6 attacks (just like S-tier), also great if your team is AD heavy since it shreds the armor for others too.
Mercurial Scimitar
If you are playing against uncleansable CC ( Malzahar, Skarner).
Edge of Night
A rare situational choice if the enemy team lacks poke that can easily break the spellshield and if they have some very important spells that can mess you up (great example: Vayne, only actual spell that she has is Condemn that could cancel your ult).
Serpent's Fang
Extremely rare situational item when the enemy team is full of shields and no one on your team can build this item.
Jak'Sho, The Protean
Solid item for long teamfights where you just wanna stay alive to do damage.
Boots
Plated Steelcaps
About 70% of the time these are your boots of choice, combine with Immortal Shieldbow and Death's Dance and you are one tanky ADC!
Mercury's Treads
Very simple; against AP heavy and CC heavy teamcomps.
Boots of Swiftness
Good against many slowing champs such as Ashe or Nasus.
Ionian Boots of Lucidity
Decent choice if you value your summoner spells, you are not buying these for the ability haste. If the enemy team has Exhaust with Cosmic Insight, these boots will help you match the timer with your Cleanse.
Berserker's Greaves
Really greedy, if you feel like you already won and don't need defensive boots. Personally I would just never go these if I care about winning.
Situational Buys
Negatron Cloak
50 MR for 900g, amazing buy against a fed AP assassin (or Karthus), can be upgraded into Kaenic Rookern later.
Quicksilver Sash
If you are playing against uncleansable CC ( Malzahar, Skarner). Can be upgraded into Mercurial Scimitar later.
Executioner's Calling
Solid item if enemy healing is becoming a problem, can be upgraded into Mortal Reminder later.
Seeker's Armguard
Stopwatch no longer exists but there might be situations where you really need the stasis effect (enemy Zed or Karthus is really fed), even though you gain nothing from the AP a well used Armguard can literally win you the game.
Elixir
Elixir of Wrath
Usually the default elixir for Samira, the AD + physical vamp just fits perfectly.
Elixir of Iron
If you need some tenacity and survivability.