Kudos goes to H4all who did this I just copy and paste and edit a little here.
The "straight" methodEdit
The first method is the regular method, or the straight method. It's very simple: one takes the high level card, or the card that you want to level up, as sacrificing target. Then we take all the cards that we want to offer as offering target. It doesn't matter whether this happens in steps or all offering cards are offered in one go.
The "reversed" methodEdit
The second method is the reversed method, used when the bonus is on. It's a little more complicated: one takes the low level card (mostly lvl 1) as sacrificing target. Then we take the high level card as offering target. In the reversed method, one should always sac step by step. If you don't, the method doesn't work. Examples of reversed sacrificing are found below, where this method is used. NOTE - After this test, H4all painfully came to the conclusion that the reversed way costs 60 (!) C's to max only one C of the same kind; therefor this method is totally useless when there is no bonus.
The Basic: Maxing C's and UC's cardsEdit
You will need 8 times the same C rarity card - example in order to fully max Gorgon in her levels you need 8 Gorgon cards in order to sacrafice and level her up to max.
The theory behind maxing the C card is to take 8 same cards. 7 sacrifices will be taking place. Every sacrifice you have to set a lvl 1 of the chosen card as sacrifice target, and you set the result of last sacrifice (thus, the high lvl card) as only offering immortal. You will start with 2 lvl 1's
This means following the prior example that once Gorgon is level using another Gorgon the resulting Gorgon is the one to be kept on adding to the other level 1 Gorgon's, keep at it until max out.
Maxing the UC's cardsEdit
You will need two max out C rarity level cards and 1 UC rarity level all of the same element. (Yes the C cards and UC cards do not have to be the same character but they need to be the same element, so example all need to be wind)
The theory behind maxing the UC is to take 2 maxed out C's cards of a certain/same element, and 2 level 1 UC's of the same element. As mentioned above, it does not make any difference whether the C's are the same or whether the UC's are the same, as long as they are all the same element. Only 2 sacrifices will be taking place in the example given, but it can be done in 3 as well. First we put our max C's into the lvl 1 UC. This can be done in either one or 2 sacrifices, but does not make any difference. The second step is to put the higher level UC, which is a result of the first sacrifice, into a level 1 UC.
Advanced: Maxing R's, HR's, SR's, MR's and LR'sEdit
There are different ways to max out your cards but the basic for to max a R card, you will need to sacrifice 1 max UC and 1 lvl 27 UC from the same element into the R.
To max a HR, there are 2 different methods. U can either sacrifice 1 max'd R and 2 max'd UC, or you can sacrifice 4 max'd UC and 1 max'd C. The difference is that you sacrifice either a R or 8 C's.
To max a SR, there are several different methods. In total, the xp value is equal to 7 max UC's and 1 max C of the same element. Remember that a HR and R have a value of 4 and 2 max UC's. U can choose to use these for levelling your SR's. It is adviceable when u want to max the cards skill as well. If the SR that you want to level will be used as evolving sacrifice or levelling sacrifice, its better not to waste skill cards on it and simply go for the UC's.
(these methods consider that the 1.5 SP is active before peforming the sacrifice).
Maxing a MR No validated information yet.
Maxing a LR No validated information yet.