Gursimran_Singh_8817
I feel like knowing the future and backstop through the anime and manga is enough of a cheat to work with when starting as a jonin. I don't think you needed to give him a system to make the MC have a meaningful impact in the story, and be strong enough to be relevant during the fourth war.
If an MC is transmigrated in a talented body or has a Bloodline, I don't think that system is necessary. But mc transmigrates into a body whose talent is ordinary, even though he knows the future but what if he doesn't have the power?.. He can learn Sage Mode but he doesn't necessarily succeed, the 3 sannin(Tsunade, Jiraiya, Orochimaru) they have more talent than mc but only Jiraiya was successful in Sage Mode, it's also not very successful
Train with a few shadow clones. Learn fuinjutsu Maybe make a chakra absorbing seal that can absorb when touching enemies like in a taijutau fight or absorb low powered jutsu. Wear weights Maybe train with might guy, 8 gates can help expand chakra. Try and ally with akimichi as their techniques are yang intensive and require chakra therefore they have a way of expanding it effectively with training and special foods and nutrients. Get the highest control you can so you wont need to use as much chakra in techniques. Use more effective and deadly techniques liek chakra flow with a sword or tanto to kill effectively and cut jutsu but maybe also skemthing like scalpel jutsu that medica and kabito used. Strength of hundred seal from tsunade seals extra chakra for emergencies aswell. Maybe get a summoning contract to learn sage mode. Hiruzen sarutobi the third hokage didnt have any bloodline. he was called the god of shinobi and proffessor due to his high battle IQ, mastery of 5 elements, mastery of bojutsu (staff), summoning contract, intermediate sealing, can repel highest level genjutsu (other than mangekyo),he allegedly learned all jutsu in konoha therefore making him insanely powerful. just a tier below hashirama and tobirama.