Short answer; run as many feeder champs with your farmer to maximum energy efficiency.

You should take full advantage of your EXP per battle.  Don't waste a slot, if you only have 2 champs you want to raise to L30, find a chicken (Uncommon 2*) and put them in.

There shouldn't be any situation in which you aren't leveling three food at a time, and all at the same level/experience.

There are all sorts of situations in the game, so you are saying it is more efficient in energy used and silver gained to level as many at a time as possible?  If that is the case then I may have to wait until I have some more.  Sure I can throw in a pack of 10 green shards also but those take me  awhile to pile up.

More at one time seems to take much longer, but maybe not in the long run.

The reason why probably isn't evident on the surface, but it is because the total experience you gain is divided evenly amongst all of the champs in the team - even if they are at max XP.

So, for example, if you were doing Brutal 12-3, the total XP you get is 17304. If you are running with one champ at max level and two food, you get 5768 XP per champ - but only two actually get any, since one is maxed, meaning you get a true total of 11536 XP. If you run with three food instead, you get 4326 XP per champ - which is less, on the surface, but the reality is the total amount you get is 12978 XP, which is 12.5% more.

The silver part is unchanged.

As for having more - use the market to buy green shards whenever possible. The silver cost is quite low. If you have the spare silver, buying uncommon champs from the market also helps, though admittedly that can get expensive fast.

good answer, and as to energy used (assuming all xp is gained by running the campaign)? Do you use less energy with one farmer and 3 champs, or (one farmer and one champ)- 3x?

Last but not least, what is your opinion on using the XP brews, are they worthwhile in the right colors?

Thanks for the help, I tried reading the ayumi leveling guide but got confused.

The former, again purely because of how the XP is divided. Taking as an example, leveling a 3-star champ from level 1 to level 30, you need 200681 total XP. With three champs, that'll take 200681/4326 = 47 runs, or 376 energy. With one champ, it'll take 200681/8652 = 24 runs in total, or 192 energy - but then you need to do that two more times, so it'll take you a total of 72 runs, or 576 energy.

Brews you should usually save for fusions, or special events/tournaments. No reason to use them any other time.

great, been wondering about this for awhile

so, all told, best to level up as many as possible at once..

That I can understand lol.

you were saying above that the silver cost for the shard route is quite low, but I am not see it, maybe you can clarify:

first, one buys a shard from the market at 5000 Silv, then summon a champ for another  500 Silv, say you get a one star or a two star champ.

The 1* champ has 1600 xp but cost  900 S to burn in the tavern.

The 2* champ has 3520 xp but cost 1500 S to burn in the tavern.

So a 1* champ costs 5000 + 500 +  900 = 6400 Silver for 1600 xp.

So a 2* champ costs 5000 + 500 + 1500 = 7000 Silver for 3520 xp.

Does not seem like a good deal.

Hopefully, you won't have to buy a lot of shards, rather winning them around the game is better, then the cost is much less, and a lucky person will pull mostly 2* shards.

What?

Are you using champs as food to level others? I never said anything about using those champs that you summon to level other people by feeding them?

You buy the shards and/or champs from the tavern to level them in campaign (or solo farming dungeons), and then use level 1 food to rank them up when they reach max level.

You should pretty much never use champs as food to level up other ones. The only exception is when you have a handful of xp remaining to reach max rank, and you prefer to use one or two 1-star champs to finish that off, rather than the 8 energy for a Brutal 12-3 run. But even there, putting aside the time-saving aspect, it's better to just run Normal 12-3 to get that last smidge of XP.