Hello my Lord Buris ... your question is a little bit confused ...

For upgrade a champion at the rank 7 (stars) ...

- i think you know that you need to sacrifice 6 champions rank 6 ...

- for a champion rank 6 you need to sacrifice 5 champions rank 5 ...

- for a champion rank 5 you need to sacrifice 4 champions rank 4...

- for a champion rank 4 you need to sacrifice 3 champions rank 3... and so go on...

You need a lot energy and emeralds if you haven't enough energy (not sapphires )...

For esample i use the auto hunt , 

- for upgrade a rank 4 you need 34 energy :

i

- for upgrade a rank 5 you need 41 energy :

i

-for upgrade a rank 6 you need 48 energy :

i

Usually i try to do this during the Tournament xp Champion ,in that way i earn some extra rewards !

If your question was refered to the Tournament Champion Duel, where the final reward is a holy bond ....than is another thing ! Also there you need a lot of energy or emeralds! 

Every Tournament Duel Champion is different than the previous , but almost always you need to collect around 7 k -8 k prizes ! I use just the auto hunt , and in every duel i collect my holy bond !

You can see some details about the Duel champion here in this link :

https://plarium.com/forum/en/stormfall-age-of-war/51_game-discussion/211957_harvest-havoc-champion-duel/

If you have something else to ask we are here, i hope i answered at your questions !

For sure there are also many players with more experience than me to give you some advice !

I wish you a good day and good game !

if by champion challenge u champion tournament in which u autohunt and gather colectibles

it takes 3.5k to 5k emeralds depending on the champion u use