Paradox Theory and Void Space are technologies that you buy in the “Science” tab.

You probably don’t want to be buying them every run. The usual approach is that most of your runs are relatively quick ones – maybe just building up paragon, maybe doing challenges, whatever – and every now and then you do a longer one for time crystals / relics / void. There’s no point getting Paradox Theory and Void Space unless you’re doing a longer run. (Aside from one special case: if you do the Atheism challenge then completing it requires you to get a cryochamber, and those require Void Space.)

It usually isn’t efficient to try to get many tens of chronospheres for “ordinary” runs: you can get more kittens per unit time, hence more paragon per unit time, by getting somewhere from 1 to 10 chronospheres + Flux Condensator + somewhere from 10k to 100k of unobtainium (and, optionally, some eludium). That doesn’t take a super-long time, especially once you’re some way into the game, and going further isn’t usually worth it.

It’s true that once you get > 67 chronospheres you can start growing resources. But note that one key resource is unobtainium, and buying all those chronospheres costs unobtainium. In order for {buy lots of chronospheres, reset} to make a profit in unobtainium, you need to be gaining enough to make up for the cost, and that means quite a lot more than 67 chronospheres.

(Also: that’s only for non-crafted resources. Crafted resources carry over according to a different formula with a square root in it, and they will decay no matter how many chronospheres you have. And, importantly, blueprints are a crafted resource and are needed for building chronospheres, so you’ll need some way to get lots of blueprints quickly in order to pull the trick off.)

The usual thing you’ll see, in e.g. “Sagefault’s Endgame Guide”, is that what you need is 8.14G unob capacity so that you can build 100 chronospheres. I think you can actually get away with slightly less than that, but that’s the right order of magnitude.

It is true that by the time you have enough chronospheres to keep gaining resources through chronosphere-resets you will have “some void and TCs and relics built up”, but that’s quite a long way into your future and you will have more than “some” of those things at that point.

My first “interesting” runs – I don’t claim that the sequence was optimal – went something like this: a unicorn-religion-based run to get 1k or so time crystals, both for buying modest numbers of chronospheres and for the 1000 Years challenge; the Winter challenge so that I never again had to worry about cold winters; the Anarchy challenge just because it was a fairly easy one; the Atheism challenge (this is a pretty slow one and you do want to have some time crystals available for it); a fairly hefty relic run lasting I think a couple of weeks, at the end of which I bought a bunch of cryptotheology buildings costing ~140M relics; the 1000 Years challenge, which I should of course have done before the relic run; a bunch of paragon grinding; another relic run of similar length. After that, an alternation between challenges (pacifism, black sky, energy, anarchy again) and paragon-grinding, and then another relic run. Etc.

You should expect quite a number of iterations of (relic run, challenges + paragon grinding) before it’s worth thinking about getting enough chronospheres to grow your resources indefinitely via chronosphere-resets.