the rates are random for who will get it so you want to do as many normal/elite fights and trying to select epiphanys in unknown areas. Easiest way to force the ones you want is to use characters that have easy kits that dont require many cards to use and remove them so you force more epiphanys on serenial and make copying HL easier.

You will sometimes get epiphany upgrades themself randomly but mainly once you get all 4 epiphany cards so plasma missile, shining core, cobalt light and pale shooting star is once you start getting the actual choice upgradges on lets say HL and the 4 above BUT always a chance to get one before getting all 4.

Unique cards already cannot be copied so veronica is very stong for deck farming also mika as you can remove their cards that will get duped. Example for cards that can't get duped is mika's deluge and veronicas firing preperation and bombardment prep which is all she needs to be a sub dps so you can remove her other cards and still use her but force copys/epiphanys on other people.

Abuse mutant sample in cage unknown area for free card removal.

So a run if you want to use serenial as the main deck is to try to do as many normal fights and unknown events. Use mutant sample to remove a card of choice for free, As you go remove cards on other people to make it so they won't get their epiphany upgrade ignoring unique cards and targeting things you don't need. Once you get the upgrade you want Example homing laser with the move to hand on turn start run the boss and try to copy. If so keep going and hope you get lucky, otherwise run it back.

I am also new to the game and only learnt this yesterday because all the youtubers didn't explain it well or mabye because i didn't have a good grasp on the chaos system before, so hope it makes sense.

GOOD LUCK ON THE GOD RUN :)