Hey,

Personally I would say Kakuzu [Earth Grudge], however Kushina [Red Hot Habanero] isn't a bad choice either, due to the fact that she is pretty cheap to get to 4*

Those are the teams i could come up with

Hope this can help u, TenTen [Great Ninja War] team will only work if u have Asuma [Windblade] skillbroken for his 60 chakra

good evening...your collection is wonderful indeed and its holding valuable ninjas which you can surely use most of them to create splendid teams...as for your summon collection unfortunately there is no given information about it..so i assume you have mostly all of the purple summons and most of the orange quality ones...i will give few team formations examples specially for your newest recruit ( itachi edo tensei ) ...hope you may find them to be worthy for you.....

scarlet blaze team

a secret jutsu users team with a great damage potential and a wonderful harmony that comes with a dangerous support....on this team your depending at the overall work of your formation members..having your main to be giving a high damage boost to your team will be giving full benefits to the formation while also being a threat to your enemy starting on round 1 with his mystery along side with itachi..which it will be making your back line to serve as a support while having the specialty to shut down your enemy lines...itachi will be a the highest threat to your enemy due to his deadly mystery and talents...a team with no protection from debuffs or immune ninjas at the front lines will be doomed by itachi...hashirama will be having an important part here...his work on the team depends on which skills you have within his talents breakthrough system but mostly having his deep forest emergence ( instant ) skill would be giving a great results with such a team surely..with him you will be able to counter your enemy barrier and boosting your formation potential...he will be a serious problem when he starting on using wood style universe to drain your enemy chakra before he trigger his standard attack...while having the right action orders and the team support on effect this will allow kushina to have a great damage boost...releasing her mystery will cause a massive damage to your enemy and triggers a deadly chain of chase attacks..holding deadly debuffs that will surely force your enemy to deal with a harsh situation..problems for you here might be barrier changers and chakra draining ninjas i think...

with such talents you will provide a wonderful combination of damage support surely..bani chakra will allow you to have most of the team mystery options starting on round 1...with a high chance to gain 60 chakra in total at the first round which it means your team is at its finest danger level starting at round 1 till 3...

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breeze dancer team

a balanced team with a wonderful damage support and with the ability to adapt under most of the battle situations...on this formation your depending on your front line to cause the damage while having the back line to serve as a support....shisui will be having an important part here since he will aid on giving you a high chance to counter your enemy auto barrier release...while giving all of your formation members the full benefits of his talents....he will be a deadly threat and specially with such a team on position 2..your enemy will mostly try to control either him or your main to reduce the danger rate of your team...itachi work will be as how its explained and he will be a problem even for immune ninjas..an enemy team that is depending on buffs or shields to win will be having a serious problem on dealing with itachi surely....your main will serve as a support specially for naruto and she will be a deadly threat with her mystery...using it on the right timing can be fatal to your enemies at fateful moments...and she will provide protection for your front lines with her clones which it will aid on reducing the damage on naruto and shisui..this will be giving them a high chance to survive for more rounds to keep on fighting till your team achieve victory....using naruto mystery will allow your team to trigger a dangerous chain of chase attack with dreadful debuffs and a harsh damage ....problems here might be also barrier changers and control ninjas and chakra draining ninjas i think

with such talents combined with shisui barrier naruto will be having a great damage boost which it will allow him to wield a deadly damage potential....natural draining talent will give you a chance to use most of your team mystery attacks especially at round 2.... which it can. allow your team to deliver a fatal amount of damage that can results on bringing the battle to an end at such an early round....

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crimson fist team

a team with a dangerous damage potential and a high endurance support....having minato to be the one your team is depending on to cause most of the damage ....while having the back line to be serving your front line...your main will be providing your team great benefits by giving a high amount of damage and endurance support to the formation..this will allow them to survive longer while having a great damage boost at the same timing ...tobirama will be here for your aid on stopping your enemy mystery release at the action orders from 2 till 4..while being a threat by himself due to his talents that boost his damage combined with your team overall support.. tobirama will be a deadly threat to your enemy..while having most of your power weight on minato... using his mystery to cause a deadly damage to your enemy while giving your team the chance to trigger a deadly chain of chase attack that can cause a massive damage and create havoc among your enemy lines that will put them under a near death situation.....problems for you here might be chakra draining ninjas and control ninjas i think....

as you see here...with such talents your formation will gain the ability to survive for more rounds and to cause a great amount damage to your enemy also...triggering minato mystery will allow you to start the chain of your team chase attack and combined with the summon you will be able to reach the final stage of the chase attacks chain....

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azure fang team

a dangerous team with a extreme damage potential and a great endurance support.....on this formation your depending at the overall team working between your members....having iruka on such a team he will be playing an important part surely..by giving all of your team members the benefits of his damage and endurance support that will rise your team potential surely...he will work just like tobirama on stopping your enemy mystery release depending on his position and till position 4.....tenten will boost the damage critical rate of your team and this will give most of the benefits to your main in order to arm her with a deadly damage support...reaching stage 2 while still having your team supporting on effect...triggering your main mystery will cause an immense damage to your enemy and it will allow you to start a chain of chase attack that is holding deadly debuffs and a great amount of damage mostly aimed at a single unit..this can be fatal specially to none immune ninjas surely....problems for you here might be chakra draining ninjas and also control ninjas i think...

with such talents you will be giving most of the support and benefits to your main in order to allow her on causing a massive damage followed with deadly debuffs..combined with your team supporting her shark bomb will be a high threat surely...

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those are all of the examples for itachi edo tensei teams...there is still alot of wonderful ninjas on your list that you can manage on using them to form splendid teams indeed.. ..i hope you may find those examples to be worthy for you and to be an aid on the times of your most need...wish for you fruitful efforts and wonderful results !.....

best of luck.....

about the suggestion on what to focus on next...if your seeking a future team for edo tensei itachi then its surely as what Aika said...kakuzu combined with itachi would be a splendid team that can. always be giving a great result...but you will have a long time till you build this team since kakuzu cant be a good position 1 ninja without a skill break i think..reaching him to 4 stars will take you a long while surely..on the other hand six path naruto will be faster to get and you can create a team for him with itachi surely...both of them can go with a deadly harmony on a team and naruto will also give you the safety from strong control ninjas...unlike kakuzu since he is always facing a threat from control ninjas....kushina is the most easy to reach 4 stars i think and specially now days since she is available on most of the hot topics events shop list...also she can reach a deadly potential of both damage and endurance after you break through her talents and she can work so well with alot of ninjas and surely to go on a great harmony with itachi edo tensei...hope this can aid you on making your decision...

Thank you all so much!