Full achievement guide can be found here:
https://steamcommunity.com/sharedfiles/filedetails/?id=29268...Although it is possible to get this achievements through excessive grinding from the beginning of the game I recommend 'finishing' the game first. With that I mean, reaching the Dragon Village and completing the story there. This alone will require lots of Dark Rituals which will help increase talent, required to get to rank level 100.
When going for this achievement, focus on the following:
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Talent! Very important and should be the largest factor. Do not Dark Ritual when your current Next Talent isn't at least 10x your Current Talent.
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Greed! Greed is an easy way to increase your Talent multiplier early on but will get more difficult but still usefull when reaching rank 90-95
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Habit! Build a party specifically focused on Habit (and save it to a template) if you haven't already. I managed to get 36M at the peak, before using the Habit Efficieny+ item from the shop.
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Routines and Envy! Use your habit on everything Sacred- and Dark Ritual related and Habit. In addition you can invest for longer runs in Global- Research Drop Amount/Chance to invest research in Greed.
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Gluttony! Auto eat Slime Jelly and whatever increases your Satiety to further increase your Talent.
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Astral World! Invest Inspiration in all Sacred Ritual, Habit and Research Drop upgrades (and in that order).
With above strategy it took me about 4 weeks and 10 Dark Rituals to reach Rank 100. I could have done it faster, but I wasn't focussing on this specific achievement. I got 35.0 Oc Current Talent when I got the achievement, but It could have been done as easily with 5.0 Oc.