Leghorns should be readily available, and as cheap as the EE from the same hatchery. Assume approval, start reviewing YouTube, Google results for homebrew starter feed recipes. Record your sources, recipes. Then select one whose ingredients are available to you at reasonable price.
In your experiment summary, indicate that you reviewed a number of popular homebrew recipes, indicate any you rejected due to a lack of {Ingredient} availability, and then casually mention that the one you did select was substantially similar to recipes X, Y, and Z from {sources}, you would therefore anticipate generally similar results if one of those alternates had been selected as your variable, instead - though with time and funding, you could repeat the experiment, using the same control diet, and additional flocks on recipes {Original choice}, X, Y, Z to determine which of the homebrew recipes was best.
You likely also want to record cost, as an alternate basis of comparison, and quantity (weight) fed, which will be needed to calculate effective cost, feed efficiency, a number of related measures of importance to raising poultry effectively and efficiently.
Ultimately, I can almost guarantee the commercial feed will result in a superior weight gain over the period, at the lowest price (both per unit time and per pound gained) - and there are tons of reasons for that we can get into later - but I'm willing to be pleasantly surprised, partially because the price of the 10# dumor is so high - I buy 24% protein feed for under $15, in a 50# bag. Trying to buy 50# of bulk ingredients, I can't begin to compete on price - the feed store doesn't carry 10# bags of oats, cracked corn, brewers grains, alfalfa meal, dried soybeans, or any ofthe other things you might commonly see in an at home recipe.