One of the least expensive and manageable sources of organic compost is vermiculture. We raise red wigglers in Tupperware totes. The maintenance required to care for them is to add produce scraps, add fresh newspaper or cardboard on top of scraps, drain the water so they don't drown, and keep them in the shade. You can read more about vermiculture here.
What you are trying to get from worm composting is a maximum amount of microbes and in order to get microbes to grow you need sugar and oxygen. To make my worm tea I use a 5 gallon bucket and add about a handful of worm casting (the dirt) to a burlap bag (you can use a sock, cheese cloth, pantie hose....). Next I pour in approximately 2 tablespoons molasses and put a source of oxygen in the bucket. In this photo I was using our bate bucket with bubbler. Now I use an old fish tank pump so I don't waste batteries. Next you want to fill the bucket with water that is not treated. If you have chlorinated water let it sit for a day outside before adding casting. Once everything is added you turn on the pump and let it sit for 48 hours. If it's cool out put it in a sunny spot. If it's really warm out place the bucket in the shade. After 48 hours you can put it in a garden sprayer or pour it along the base of plants. I like to spray with worm tea so the microbes cover the foliage. The microbes will handle fungus problems and can deter bugs from munching on leaves.
I also make compost tea out of rabbit manure and chicken manure. My favorite source for fertilizer is rabbit manure. It's so simple! Rabbits usually use 1 or 2 spots in their cage to go to the bathroom making it easy to collect manure. Rabbit manure also breaks down very quickly and is not too "hot" for plants, meaning it won't burn plants by adding it to soil without decomposing first. I simply add the manure to a bucket of water, stir, then pour over plants. I allow the tea to go on the foliage as well as the soil since it's a milder form of fertilizer.
My other source of fertilizer comes from the chickens. Chicken manure that is not decomposed first can burn plants so I have found the best way to make chicken manure tea is to grab a handful of composted manure from the compost pile and place it in a bucket with water. Next I add a handful of fresh manure directly from the coop. I stir it until dissolved and pour a small amount to the base of plants. This is a much stronger fertilizer so I don't recommend pouring directly on leaves and it's important not to over fertilize. A 1/2 cup full at the base of mature plants and an even smaller amount around newly sprouting plants has worked well for me.
How do you fertilize your garden? I would love to learn ways you have had success!