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I've been kind of following whatever SequenceTT2 tells me to upgrade, but not religiously. I sometimes level a relic more than it tells me to, and so on. As far as I know, it's the best way while also being very convenient and easy to use.
The one you're talking about is called SequenceTT2. An app on Google Play Store. Follow the link I think you'll see the screenshots you're talking about.
There's an app called 'SequenceTT2' - [link]
Install it and export your artifact csv file from it - that's your second .txt file.
Sorry that my explanation is not clear enough haha...
If you play on Android the Sequence TT2 app has a simple description of all artifacts under the Artifacts tab, for instance here is Book of Shadows as "relic multiplier".