Okay, in Naruto we know that summons are slightly different to how they are set up in game, so I think we should change this to make it more like the series.
First you would need to learn Kuchiyose no Jutsu, this could be something easy, like Iruka or someone else at academy.
After this you would need to make a contract with a certain group, Toads, snakes etc...
When you have a contract you then have to earn the respect of the various summons in that group, before you can summon them, like when Naruto had to earn Gamabunta's Respect, or Manda demand 100 human sacrifices.
Once you have done that you could summon these summons in battle as a companion, such as Kage Bushin, Suna Bushin and other things, at a chakra cost.
Also I think each line of summons should have something special to them, which I go into later.
Now this makes it more like the series, not everyone has a summon, actually not many do. Also the summons have a chakra cost, just like in the series, meaning they can only use them when they have to. Also it takes time and effort to get the summons, which it does in the series, they don't simply pay a fee, then get unlimited use of them for the rest of the day.
Now that I've had my rant, I'll show you some examples of what these Summons could be, I have giving them all a sensei, a list of summons for the groups, and I cost for each one.
Then there is a something special that each line has.
Toads:
Sensei - Jiraiya
-Gamariki(cross dressing toad), maybe? (1)
-Gamatatsu (1)
-Gamakichi (2)
-Gamahiro (5)
-Gamabunta (6)
Specials - Toad Specialty
-When you kill Oro you can choose the 'Toad Hermit Arts' Specialty
-Tōton Jutsu - Transparent Escape Technique (1)
The enemy can't see you for 1 round, Invinsible.
-Kaeru Kaeru no Jutsu - Toad conversion (3)
'Turns' enemy into a Toad for 3 rounds Lowers Atk and Def.
-Gamadaira Kage Ayasuri no Jutsu - Toad Shadow (5)
You hide in the enemies Shadow and control them for 5 rounds, lowers atk and small damage.
-Kuchiyose: Gamaguchi Shibari - Toad Mouth Bind (9)
You summon an Esophagus of a Toad in which you fight, last until Enemy dies, Lowers Atk and Def.
-Katon: Gamayu Endan (11) (Only with Gamabunta)
Gamabunta sends a blast of toad oil from his mouth and you ignite it, 2 rounds, Big Damage.
-Kuchiyose: Yatai Kuzushi no Jutsu - Food cart destroyer (2-12)
You summon which ever Toad right on top of the enemy, causing damage and summoning the Toad
at same time. Cost Double normal Summoning cost.
Dogs:
Sensei - Kakashi
-Pakkun (1)
-Bull (1)
-Shiba (1)
-Bisuke (1)
-Akino (1)
-Guruko (1)
-Ūhei (1)
-Urushi (1)
-Ninken(All 8 at once) (10)
Specials - Tracking/Multi-Summoning
-The ability to summon one at a time, or to summon all 8 at once at a greater cost.
-Kuchiyose: Doton: Tsuiga no Jutsu(14)
Also can summon all 8 at once and gives enemy a debuff.
-Add a link in the forest where you can summon the dogs to use their tracking ability
to find where someone is sleeping for a small chakra cost (2).
Snakes:
Sensei - Orochimaru
-Kyodaija (4)
-Manda (10)
Specials - Defensive Snakes/Power
-The ability to summon the Snakes as a shield, protecting you from damage.(3)
-Manda is very powerful compared to other mounts.
-Maybe able to summon the Rashomon gates. One (5), Triple (15)
Slug:
Sensei - Tsunade
-Katsuyu (1-max chakra)
Specials - Healing/Chakra determine strength
-You chose how much Chakra to put into Katsuyu, which determines it's strength when summoned.
-Katsuyu Daibunretsu (3)
Can divide into smaller slugs, then reform if needed. When smaller slugs they will become a healing buff.
Monkey:
-Enma (6)
Sensei - Third Hokage
Specials - Weapon
-Henge: Kongōnyoi(4)
If Enma is summoned, he transforms into your weapon, making it a level
16 Weapon called Kongōnyoi. He can transform back into a companion returning your weapon to
normal afterwards.
Other possible Summons:
Weapons,
Puppets,
Kamizuru clan's Bees,
Kamatari,
Ninkame,
More...
This is just an idea, feel free to say 'yay' or 'nay' also any other ideas are welcome.