'Beaus daddy' - the best advice I was given a very long long long time ago - was fed your pup what the pup does best on - and more importantly - what you can sensibly afford !
The absolute best way to fed your pup is via Newsfie's way - RAW. But what I have found, particularly in my situation - is - that I do not have the knowledge - and - more importantly - the time at present - to be able to do it properly !
I feed BlackHawk - as others do - it is an Australian Company and all natural - so - ticks heaps of boxes for me ! So I base the feeding of my pup on that - then add other stuff. The cost is surprisingly not that exorbitant - when you work it out on a weekly or daily basis. A 20 kg bag for my one and only lasts a min of 60 days. So do the maths !
Also the better the dried dog food is - the less your pup needs - and - less that comes out the back end !!!!!!
So what does this BD eat - all and everything that is offered. There are no fussy eaters allowed in this place ! If the nose goes up then so does the food ----- until next time.
I don't leave food out for the pup for when he feels like it - to tide him over before his next meal ! This really leads to having a pup with fussy eating habits.
Riley is fed 2 times a day - by me - morning and evening.
He gets BlackHawk as the base - plus - either - and only 1 at the time of the following choices - such as - sardines, mackerel, tuna, salmon (all in spring-water - no oil), and frozen vegetables (heaps of choices here - but pup likes the mixed) from the supermarket.
Take care changing the diet of your pup too quickly ! It really needs to be gradual - or you will see it coming out the back end - which is not pleasant for you or your pup !
I have friends who have GSDs and they do really well on SuperCoat Sensitive - but they also add to the dried food.
Have a look around where you live, find a good butcher and make them your friend - I scored chicken carcasses on Friday for $1.99/kilo from my local butcher - plus I bought other stuff for the 'hoomans' and got the bones for the pup for free !!!!
Good Luck !