The #1 key to successfully saving money with your garden is to keep expenses low.
The unique thing about home gardening is that your financial savings are pretty much guaranteed to be less than your grocery bill because no matter how much you produce, somehow, you have to eat it to realize a direct savings.
To save more money, you either have to eat more of your own produce or grow your produce with less money.
Even if you have a large family and are able to cut your grocery bill by half during the harvest months, you might still only save about US$1,000 even in a good year, depending on where you live and how you eat.
Unless you are a vegetarian family with 10 kids who love salads, live in the Pacific Northwest, have a neighbor who loves to give away free compost, and have prior gardening experience, you will likely save a lot less the first year, even before you deduct your expenses. In fact, you would do well just to break even.
My point? Keep your total expenses under US$200 the first year if saving money is your main motivation.
Here are some tips to get you thinking.
Seed and plants
First and most obviously, you will need seed. I would suggest you buy heirloom seed and carefully select a few varieties to try based on your tastes and your region. Learn to save your own seed and then next year, you can swap seeds with other gardeners to experiment with other varieties until you select ones that really do well for you. You can expect to spend at least $30-50 just for seed. You can easily get carried away and spend a LOT more.
You can get cheaper seed at your local discount store if you are willing to get varieties that are factory farmed and generally not quite as appropriate for the home garden.
If you buy plants, your costs will go up dramatically even as your choice of varieties vanishes. If you grow your own transplants, you will probably need a cold frame and a bit of growing skill.
Garden space
You need someplace to plant.
If you must garden in containers, you can get the cheap black plastic pots greenhouses use.
A lot of people will just dig up a spot in their yard. Choose carefully, and find someplace that is well drained, not on top of the septic tank if you have one, gets appropriate sun, is away from tree roots and close to the house. Also, a lot of people have parts of their yard that have better soil than others. Unless you are just wanting to improve a section of your yard, you will likely want to choose an area that has better soil. If you can avoid buying timbers for raised beds, hauling dirt and so forth, this might not cost you anything.
Digging
You need something to dig with. Even the permaculture and Ruth Stout type people will probably want to dig up their soil the first year or even two. For some gardeners, this means a powered rear-tine tiller, for others it means a hand trowel. Most people would do well to get a good digging fork as their first tool.
Personally, I would buy a digging fork before a shovel. It is the best tool available for my preferred system, biointensive raised bed gardening, and is a lot easier to use for ground breaking and double digging of raised beds than a shovel. A shovel is pretty important too, but you could likely get away with just borrowing one from time to time.
A quality digging fork could run you as much as US$60. A shovel should cost less. If you take good care of them, these tools should last for many years.
Transplanting
You almost certainly want a hand trowel. Again, I would suggest quality here. Otherwise, you will end up doing like I do and replacing it every year or so after you bend it. A trowel is useful for transplanting into the garden and working with small plants. It can also be useful for stirring up a small patch of soil for replanting. Most gardeners find this tool indispensible.
Cultivation
You need something to cultivate with. This is highly personal and depends on your gardening style and type of soil. Some people have a favorite hoe. Others use their trowel. Some just mulch and pull any weeds that make it through.
If you are a new gardener, don't sweat it. You will likely go through several tools before you find one you really like for your style of planting, choice of crops, and soil.
Plant maintenance
You have to maintain your plants. This means water, fertilizer, mulch, and soil amendments as well as pest, bird and varmint control.
If you live in a dry area and pay a lot for water, you will want to look for varieties that produce with little water as well as planting methods and spacing that reduce water use.
Having a compost pile can help with your fertilizer needs, but it takes a minimum of several months to make compost. Most manure also needs time to age.
My experience
I grew up gardening, and when I moved to our house here in the Dominican Republic, I wanted to start a garden. To do it, I had to break up a cement pad, pick through cement-like construction fill, haul soil amendments, buy soil, buy boards and cement to fix the borders of the beds, and pay for water.
Even then, I have had trouble growing things and have experimented unsuccessfully with a long list of varieties over the last three years. A few have been very successful, but now we are anticipating a move this summer, so I will have to start all over again.
I have learned a lot and had some fun doing it, but I doubt seriously that I have saved any money.
The bottom line
If you are a new gardener or new to your area and can break even your first year, you are doing pretty well. If you can set yourself up to double and triple your production and consumption the second and third years while spending a very minimal amoung on seed and supplies, you are doing great.
Gardening is a skill that has to be learned, and each gardener has to learn their own garden, build up the soil, figure out what their family will eat and what their local pests will eat.
Of course, saving money isn't the only reason to garden…
—Luke