This usually boils down to what you can afford.
There are lots of members with different incomes.
Some can afford the very best £40 - £80 for a 13-15kg bag of food
Others can only afford, whatever is available at the local supermarket.
If you can give a price range you are happy to pay then we can give advice on the best in that range.
However as a general rule of thumb, look at the ingredients.
You should always be looking for WHOLE ingredients,
corn, not corn husks,
meat, not meat products.
If it says "meat product - 12%" then the "meat" could be anything, skin, hooves, offal, hair.
as opposed to it saying "Beef - 12%" where they are stating REAL meat.
Hope this helps.