Any map for Super Love Potions, -MAGNUM-.
Try and only breed monsters that won't require Super Love Potions for a few days to save up the ones you get in the next few days.
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With regards to the sacrificing of monsters, Epic rank monsters will offer more percentage for blessing. a Level 10 will give 10%, level 15 yields 17%, 20 gives 20%...40 gives 30%, etc. i.e. for every 2 levels after level 10, you get 1 extra % for blessing.
If you bred monsters before, sacrifice those.
Note though that you might need that monster again later on so it will be a good idea to leave a low rank male and female of that monsters, if you need it for synthesizing later. Obviously, don't sacrifice the best ones as well.
Level them up to about level 20 each and you'll only need 5 for sacrifices! Level them all to 30 and you'll only need 4! I think 40 will be a waste of your time. My suggestion is to just go for 20 if you have a number of monsters you'll allow to be sacrificed.
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What superfly said should be noted. It's better to get a male and a female A- or so, right before you will need a super love potion. With blessing, then, you'll only need 2-3 breeds for an S monster.
Good luck!