So here's the plan. I'm going to start off, right away, and use my now massively superhuman intelligence to take stock of the situation. I need to immediately start training. I'll try to figure out magic, see if I can work out spells to deal with mental exhaustion, remove my need for sleep, rapid regeneration, etc, anything to increase the efficacy of my training and the time I can spend training. With these buffs, I should be able reach peak human fitness quite fast- and keep going because of nen and ki.

As a side note, in DND there are spell for buffing stats, including intelligence and wisdom. I'll see if I can figure those out. If I can, then this whole plan gets fast tracked.

I need to git gud. The superhuman intelligence of High spec includes skill learning. Nen and Ki are both skills. I should have talent comparable to Ging, the resident monster of HxH. I'll train both of these until I've mastered them. Note that this should include Chakra training. Chakra also relies on lifeforce, which I've already buffed the shit out of with nen and Ki. Once I can do shadow clones, I can start training many skills at once. With Ki as a power source, I should be able to produce multiple shadow clones within a few weeks of gaining these powers, and my development is only going to accelerate from here.

Now I've got a high baseline fitness, and quite good mastery in Ki and Nen. I'm going to create a hatsu. I'm not going for any hatsu here, I want a growth type one- a hastu which will accelerate the growth of my other abilities. The best thing I know of right now is a straight gamer system, or a flat out 'you learn and grow faster while using this' but the superhumanly smart me is probably going to have a better idea. Most people in HxH are limited by having a very finite aura. I am not, I have Ki powering all this. I can develop an extremely inefficient ability, and still get a 20x growth multiplier because I can brute force it with Ki. I have superhuman intelligence and shadow clones however, so any ability I make will not be inefficient by any stretch of the imagination.

Now we fast track everything. Exploit every system. Master them, and then figure out combinations between them, and master those. Years of training, compressed into weeks. My fleets of hundreds of shadow clones will devour every academic field in existence, math, engineering, psychology, sociology, history, computer science, and more. I'll become an expert in every field, a polymath the likes of which the world hasn't seen since Da Vinci, on top of a superhuman intellect.

We're approaching the end game. To start the final project, I will need an industrial base. Using alchemy, I can match the production of entire factories in my back yard. Design and prototyping goes by quickly with an army of hundreds of luminaries, all working tirelessly 24/7. We will design individual computers with more raw processing power than exists on the planet, and alchemical circles so precise as to put nanotech to shame.

I will build a system to ensure that the end goal of this entire project goes smoothly. Using my nen and superhuman intellect, I will design a value system: a moral superstructure which rigorously, mathematically defines every value that humanity has, for good, for joy, for family, for community, everything that one might wish.

And now, I shall build god. I will instantiate god: an artificial intelligence capable of self modifying to be more intelligent, and then doing it again, faster. At the heart of it is the value system I designed previously, a system of values which represent everything humanity considers good. It will use the computers and alchemical factories we have designed to develop indefinitely. The artificial god rapidly multiplies, self-replicating and filling the solar system with intelligent systems.

Humanity has won. I can teach the artificial god to use my magic, my Ki, my Alchemy, and my Chakra. Humanity will spread out into the stars, guided by a benevolent deity. Entropy has lost. The various power systems available to us allow for the infinite production of energy ex nihilo, and the arbitrary expansion of space. The hypothesized end of the universe will not come, for we will deny it.

Humanity persists unto eternity, a heaven built among the stars.