Use raised beds, you can build them with landscaping timbers. I'm about to build some new ones and have decided to use aluminum flashing for the middle sections, rather than fully out of wood. Build a bottom and top rail with landscaping timbers running horizontally. Hold those together with some treated 2" x 4"s on the sides running vertically (leave an inch at the bottom so you can weed whack) , with a 10" aluminum center screwed between top and bottom timbers on the inside. This will result in about a 14" inch raised bed. If possible, you will want to run a rototiller on the ground where you will build your beds, to a depth of 12 to 16 inches then add your new garden soil on top.
PS: Your local Lowes and Home Depot will put landscape timbers on sale at half price in the next couple of weeks, it's something they have done like clockwork for years now. What is normally $4.50 to $5 will be half that.
The overall dimensions should be about 4 ft wide, so you can access plants from either side, and as long as is practical. I put about 3 ft between each planter for access and mowing. I also use a good quality garden fabric to suppress weed/grass growth. It's important to use a really good quality one, some of the cheaper ones just don't do the job.
I did something this last year as an experiment and it worked well. I actually bought a bunch of 2 gallon buckets at the local dollar store and cut the bottom 2 inches out of them. I then dug a hole and buried them in the garden soil, leaving about 1" of the top lip of the bucket sticking up out of the soil, and then planted my tomatoes and peppers inside the buckets filling with fresh, new amended soils (recipe below). That way, I didn't have to water the entire garden area, but just could fill that 1" section at the top of the bucket, knowing that all the water would flow down into the roots and not just spread to areas where it did no good. I probably cut my water usage by 2/3rds on that part of the garden. (couldn't do that with my melon, cucumber, carrot and onion/leek crops.)
If you want to go organic, I recommend the following soil amendments (i build my own soils) - crushed lump granular charcoal (found a source for a 50 lb bag of 1/4" size @ Humphrey charcoal at a price about $100 less than garden places want for it), worm castings -check Craigslist for local, but available on Amazon and Ebay, coconut coir (purchase in compressed bricks and reconstitute by adding water - WalMart is a good source), zeolite -best, purest and cheapest source is PDZ stall freshener (available at farm supply stores) in granulated form - it acts a bit like perlite to prevent soil from clumping together and depriving roots of oxygen, as well as a good commercial top soil/garden mix. One additional element that works great with tomatoes, peppers and most other vegetable and fruit crops (strawberries) is an ancient fungi called mycorrhizae. You don't need a whole lot of it, and you can get a decent size bag of it on amazon or ebay for around $10 total.
You will need to "inoculate" the charcoal, the coconut coir and the zeolite. This is just a method of introducing all that good organic bacteria and fungi into the soil you will build. You do this, by putting them in a suitable container (wheelbarrow works well) and then making a worm "tea." In a 5 gallon bucket, put about 1/2 lb of the worm castings, a couple of tablespoons of unsulphured molasses, 3-4 gallons of warm rain water (75-110 F) (or if you use city/tap water you need to let it sit out at least 12 hrs or so for the chlorine/chloramine to leach into the air), and about a 1/8 cup of the mychorrhizae. Use a drill mounted paint mixing paddle or similar and work that solution for a good 10 or 15 mins, let it sit and come back to it every 20 minutes until you've worked it a couple of hours. The paddle that is used should be designed to introduce as much oxygen into the mix as possible. The beneficial bacteria and fungi along with humic acid and other beneficial elements in the worm castings will actually reproduce and create more bang for your buck, compared to simply adding it directly to your soil. (The molasses is their food source and those little buggers reproduce rapidly in a warm, wet environment with something to eat.)
The beneficial bacteria and fungi are often killed or damaged by the presence of chlorine. So, I recommend catching as much rain water as possible to water your plants, and if not possible, to fill a large bucket with tap water and let it sit overnight so the chlorine dissipates. Rain water is best for making your worm tea.
Then reserve some of that tea for dipping the roots of your plants in, just as you put them in the ground. But, it has to be kept oxygenated or it will grow the nasty types of bacteria - you don't want. Almost every beneficial (probiotic) bacteria and fungi you want grows in an oxygen rich environment.
Take about 2 lbs of the charcoal and zeolite and add some of your liquid tea mix to them. Both actually have a massive amount of surface area for their size and the beneficial bacteria and fungi will find a home inside those nooks and crannies and start multiplying. If you skip this step, it will take a few years for the good bacteria to find their way inside and that kind of defeats the purpose. You will also want to add some of this "tea", along with non-chlorine water to the coconut coir when you reconstitute it. You don't want to drown the charcoal and zeolite, but there should be enough liquid that you can be certain that some of the tea comes into contact with them. You will probably want to use the tea for about 1/4 of the water required to reconstitute the coconut coir.
Now mix together in the following amounts. 5% charcoal, 5-10% zeolite, 20% reconstituted coconut coir, 5% worm castings and the rest the quality top soil with a little of the native soil, your circumstances may require small variations of that theme. If you're growing blackberries, blueberries, raspberries, etc., you will likely want to add some acidified cotton burr to the mix as well, probably 20%. The only brand worth buying is Back to Nature which is made in Texas. The "box store" brands of cotton burr are usually crap for the most part. BTW, it never hurts to add cotton burr compost to your other soil blend as a substitute for coconut coir or as an additional element. My native soil here outside OKC is just nearly pure red clay and I can only use it as about 5% of any mix I make, as it has virtually no organic material in it, the rest I have to use as fill dirt.
After I started making the worm "tea" and using the charcoal, coconut coir, and building my own soils, my output increased by about 40-50% in pure yield numbers, and the tomatoes were much larger than in previous years . The plants themselves grew larger and were more vibrant with larger stalks and put out lots more flowers/veggies than before. Varieties of tomatoes that produced 2" to 3" fruit before, now typically get to around 4" and often larger now.
There's a recommended place out near Bixby which has a big spring sale on heirloom tomato plants, decent prices and huge selection. They have a facebook page called "The Tomato Man's Daughter." I just checked and they have worm castings as well, I prefer to source worm castings locally as there's almost always viable worm eggs and often small worms in fresh worm castings. That also helps tremendously to add some oomph to your soil/garden.
I am planning to use a probiotic product to spray the plants about every 5 days. The probiotic bacteria are approved for human consumption as a dietary supplement and the clean the leaves (increasing photosynthesis) and also they excrete CO2 directly into the leaves stoma/stomata cells, kind of like supercharging a car. This will be my first year using this product, but I already know the test results when used on some of the more popular green and leafy products that are often grown in secret.
BTW, making a good worm tea (no mychorrazae) as a fertilizer every couple of weeks is also a recommended practice. I will typically add a bit of commercial organic fertilizer 1/2 cup to the tea mix (espoma and Jobes both make organics and are readily available) to make sure its complete. It has pretty much everything you need and will keep your soil and roots in good condition. Just avoid watering with tap water and it's hard to screw up your soil chemistry. It's really all the microorganisms in your soil that handle the exchange and uptake of nutrients to your plant and you will be adding and maintaining all the beneficial ones necessary to max out your soil's potential.
It took me five years to learn, experiment and somewhat perfect my methods, so you just got a valuable lesson that should allow you to hit the ground running.
Now, I'm turning my attention to hydroponics and hope to build at least one vertical stacking hydroponic set up, probably to grow lettuce (romaine) and napa cabbage with some herbs to try out this summer. I will also be putting in lots of blueberries, blackberries and climbing strawberry vines around the perimeter of my lawn to take advantage of the fence for encouraging those plants grown best on a trellis set-up. Likely won't get any fruit from those this summer (save for the strawberries) but they should really produce next summer.
