Stage one: Instead of using actual wizards, use perfect autonomous illusions of yourself. Does this require reverse-engineering the actual Thassilonian spell from the decayed version practiced in modern Golarion? Yes. Will you blow yourself up doing this several times? Yes. Will you blow up these tremendously expensive perfect autonomous illusions that cannot be resurrected or (except at great expense) repaired? Well, occasionally.
Stage two: The country can take a little magical spillover, right? Horrifying crop blights, new mutant plagues, trees eating people, these are just hazards of life in the post-apocalypse, right? Nobody will even notice you're doing it. Right, that's what you thought. See, all these "secondary balancing circles" are completely superfluous, just perfectionism from an ultra-rich society.
... Okay, most of them are. The quinary ones, definitely. Sure.
Stage three: Once you have enough ritualists (see: copies of yourself), hack together a ritual (see: blow yourself up several times) to instill complete confidence that YOU ARE A GOD and absolute obedience in any wizard who already has the vague generic belief that you might sort of be a god, as well as terrifying divine powers from shards of dead gods or whatever you found lying around. Then, leverage this to get more wizards. Repeat until you have a sufficient ritual magic team to carry out a ritual to turn a preexisting cult into Actual Ascension, by conquering the planet if necessary.
... Actually, no, that's step four. Step three is building a fortress.
Okay, step three might be conquering a country -