So my build works in a way that you Synergies with yuumi so if you followed what I've posted you are supposed to get some Solid Gameplay + that build will be efficient only if it sits right with your playstyle(and if you have yuumi support) because remember there are a lot of play styles out there.

Ok so first is a decent starting item since early you will focus on getting the farm but it doesn't mean you will be passive because if you have the chances to punish your enemy and poke them then do it.

++ you should of course add a health potion and the Stealth Ward.

I suggest you to buy Sheen when you can since it will help you to deal more damage while getting stacks for your ult.

this is the first item you should rush for, for the people that would ask why since the essence reaver actually refunds you your mana and even adds more when you use your Q as Samira it means most of the times when you will poke while trying to find a good way to enter and kill the enemy team you will have almost constantly full mana which helps your support because you will be able to give them the blue so they will spam their abilities.

About The Boots: Some people would rather buy boots after the first item but it depends on your playstyle.

ok so the Second Item you should rush for now is after building the essence reaver you now supposed to deal at least 160 damage after using an ability which now leaves the chances of you entering a fight whether It happens at the Baron area or at the drake area your surviving rates depends on the shieldbow and in your support(best support for this is yuumi) the shieldbow adds a good amount of damage to your attacks + since most of your abilities can actually crit it means that with 2 items you now have 40% chances to hit crit hits with your abilities.

Third item is Phantom Dancer is a good for this build because of the unique the item has and the way it stacks, you can stack it on minions & turrets & jungle monsters and champions which gives you movement speed and the ability to walk through units and after gaining 4 stacks(4 basic attacks within 3 seconds) you gain 30% bonus attack speed which is great for gaining ult stacks with samira

your fifth item should be The collector is overall good for Samira because it gives you some Armor penetration and executes enemy champion when they are under their 5% max health + it will give you 25 more gold which will get you close to the last item a lot faster :)

and after all of that your last and final item should be for a few reasons it adds a lot of ad which you need + makes your crits a lot more stronger which will help you in the late game to deal more damage to a more armored targets.

My rank is platinum IV in EUNE so I wont brag about anything but in a match that I played with a friend using my build we got to
which in my opinion is a pretty good since we were able to 4 vs 5 so it shows you can carry with that build :)

Is a good extra item incase you do not want to go with one of the items I suggested you to go for since it stacks with your ult and helps you to deal a lot of extra damage!