Just play the game. Explore. Find cool stuff. Reset with Concrete Huts and 130+ kittens.
This is already covered very well elsewhere. See especially Monstrous Advice.
The defining feature of mid-game is chasing relics. They unlock antimatter, spending void, and time skipping. You first get them (rarely) by trading unobtainium to the Elders.
Recap. You should have:
Since you have Numeromancy, if you run a festival during the Redmoon cycle, you'll get nearly 2.5x your unobtainium production. With a Chronoforge, you can shatter time crystals to skip the non-Redmoon years. With a reasonable outpost count and Space Manufacturing (backed up by as many elevators and factories as you can afford), you can easily turn a profit on time crystals and relics by skipping those fallow years. Summary:
Next it's time to research antimatter. Build sunlifters and let the skips you're already doing bring the antimatter in. The key upgrade is "Relic Station", which gives you 0.01 relics per space beacon per game-day. They will each give you 432 relics per RL-day, which isn't exactly fantastic, but there are ways to boost it. Summary:
Once you can get a hundred unobtainium per second (outside of the redmoon cycle), it's time to switch engines. Build a couple resource retrievals, usually 3-5 will do it. The plan is shatter a crystal, get a dump of unobtainium, and trade that to the Elders for more than one time crystal. Build markers and feed necrocorns to improve your ratio. Build chrono furnaces to skip more often. I usually try to get 37 CF and 20 RR. Spend some time offline to get 6500 flux and buy Chronosurge, then you can spend most of your time moving at 1.5x speed. Always stockpile up to 9500 before you reset so you can buy it again without waiting. Summary:
When it's time to end the run. Just start shattering past the chronoheat limit. Keep going as long as you're making a profit. Then, once you're at the end, enable furnace automation and watch as all that stored chronofuel propels you way into the future, and spits out mass resources due to RR. Don't forget to sacrifice alicorns before you reset.
Late game is all about chronospheres. The final goal is to reach at least 8.14 billion unobtainium capacity. With that, you can build 100 chronospheres, and reset at full capacity to leave you with 12 billion unobtainium. Building 73 chronospheres costs just less than 1G UO, and, on reset, increases your stockpile by over a 1G, meaning that every reset is at a profit. Ignoring time crystals and blueprints, of course.
Unobtainium capacity is hard to come by. Only two things give it:
So, on the final run to 100 CS, you want to have a lot of burned paragon, antimatter for sunforges and AI cores, and void for rifts. As well as as many event horizons as you can muster. Reasonable estimates are:
Now, a point of optimization: Having a large antimatter/void stockpile doesn't help getting paragon, but having lots of paragon does help building a stockpile, so that suggests the following order:
Paragon grinding is well covered. See https://www.reddit.com/r/kittensgame/comments/hu8n43/late_game_short_runs_for_maximum_paragon_grinding/. I prefer pushing to 5 CS and getting the flux condensator. Especially with the boosts given by all that paragon and cryptotheology, I think it works better.
The long run will focus on maximum energy, containment chambers, and heatsinks. Once you've got all you think you can handle, sell all the storage, and switch over to a regular shatter engine. Max out chronospheres and farm void.
Third, is "quick" chronoresets. The goal is to build a short shatter engine, but use the unobtainium for building chronospheres instead of trading. Given the large storage given by the unburned paragon, you should be able to reset pre-dark-future at a profit. Do occasional two-day time crystal runs to keep enough on hand.
End game is about overcapping resources and chasing Infinity. The idea is to build 70+ chronospheres and reset, only fast. We can do it fast because after resetting with 100+ CS, we can now build chronospheres out of the unobtainium/science profit we make resetting. Time crystals are a known problem, but there should be enough. If not, import a save during the 100 CS run and get some more before the reset. The main problem is blueprints. There are three ways to get them, and each is useful in turn.
If catpower is lower (and it probably is) hunting is the best option. This eliminates the possibility to grow catpower, but everything else will go up. Build housing, tech up, get solar revolution, all kittens hunt, craft the blueprints, build the chronospheres.
Once you have large enough stockpiles to be able to make it work, switch to mints. This doesn't spend catpower, so you can start growing it. Mints work based off maximum catpower, and the best way to get that is temples and templars. Build those, and cheap housing. Don't wait for kittens, build mints, make furs, craft the blueprints, build the chronospheres. It's possible to reset every couple minutes.
Finally, once you have a large enough stockpile of catpower, switch to trading. This is the fastest reset possible. Set ctrl-click to be a suitable number for chronospheres. Workshop, flux condensator, explore, trade, ctrl-click chronos, reset. Loading in should take longer than doing the reset. Relatively quickly, trading will give enough blueprints to pay for multiple resets of chronospheres, even with the square root. Swamp the 10% trading loss by building lots of chronospheres, over a thousand is reasonable.
A good bench mark for when you can transition to trade is when you can make 88 Chronospheres off a single trade. That takes 376 million blueprints, which means 3.76 billion trades, which takes 188 billion catpower, which is 20% of 940 billion catpower.
One resource that can still be pushed higher is paragon. There are three reasonable ways to generate unreasonable amounts of it.
First, lots of beer:
Second, mass shatterings:
Third, the cryo engine: