Feeding horses properly and well is almost an art form. I am not going to dictate to you on this blog what exactly to feed your horses because it is different for each horse what they like to eat and what they can eat. What I will do is tell you how to go about feeding your horses so that they are able to do whatever work it is you want them to do.
I recommend John Konke's book "Horse Nutrition in Australia" for Australian readers. This book is very thorough and is for Australian conditions. I would also recommend you discuss with your vet whatever diet you feed your horses, so that he can recommend adjustments if necessary. Also it doesn't hurt for your vet to be aware of whatever you feed your horses so that it can be a consideration when he has to treat them.
If you live overseas, take the time to read up on what is best in your area to feed your horses.
Cheap food is not necessarily better even if it helps stretch the budget, but then again, you don't need the most expensive feed either. Seek advice from knowledgeable people around you, even if they have different breeds of horses to you.
Horses are grazing animals and their first preference is for grass and grass products such as hay. This also includes chaffs, which is grassy stubble left over from harvesting. As such if you notice your horses eat best when their heads are near the ground. So when feeding horses it is best to put a bucket with their food on the ground, tied if necessary. My boy used to pick up his bucket after tea and throw it all around everywhere and have a grand old time doing it. Needless to say we went through many buckets. Drinking should also be as close to the ground as possible.
When feeding hay, a hay net at its longest without being actually on the ground is suitable. If you put the hay on the ground directly, unless it is on grass, will mean the horse will pick up dust and dirt from the ground. Dust and dirt in the gut after a while will cause colic.
A salt lick is a terrific additive if your horse will lick it. We wet down our horses' feed as they have a tendency to choke on dry food for whatever reason. So we cannot put a salt lick into their food bin. We add a powdered vitamin and salt suppliment to their food, but this is more expensive than a salt lick. Salt is vital to horses.
Water should be fresh every day or free flowing if they drink from a stream or creek. Make sure you are aware of what is upstream from streams and creeks, as you don't want poison running off - even fertilizers from the ground are not good. Likewise if drinking from dams.
Carrots and apples are good suppliments to put in their feed. Molasses will help if food taste does not meet with your horses' approval. Carrots and apples are much better treats than sugar lumps.
Sugar will rot horses' teeth in much the same way it will rot human teeth.