People overthink this one. You do not need a dedicated bed, a plan on paper, or good soil. You need a few square feet that gets sun and a hose that reaches.
Here’s how I’d start if I were starting over.
Sun first, everything else second
Most medicinal herbs are Mediterranean in origin, which means they evolved on a dry hillside in full sun. Six hours minimum. Eight is better.
If you’ve got a choice between a spot with great soil and four hours of sun and a spot with terrible soil and eight hours, take the sun. You can fix soil. You can’t add daylight.
Start smaller than you want to
Four feet by eight feet is plenty for a first year. That’s enough for eight or ten plants, which is more herb than you’ll process the first season.
The failure mode here isn’t planting too little. It’s planting a thirty-foot bed in April, losing it to weeds by June, and deciding you’re not a gardener.
About Alabama soil
If you’re gardening in the red clay a lot of us have here, you already know it does two contradictory things. It holds water like a bowl when it’s wet and turns to brick when it’s dry. Most herbs hate both of those conditions.
Two ways around it. Amend the clay with compost, and keep doing it every year, because one application won’t get you there. Or build up instead of digging down, with a raised bed or even just a mounded row, and fill it with something that drains.
Raised beds are the shortcut. If you’re on heavy clay and you want to skip the multi-year soil-building project, build up.
What to plant the first year
Pick things that are hard to kill and that you’ll actually use.
Easy and useful: chamomile, calendula, lemon balm, mint, thyme, oregano, yarrow.
A little fussier but worth it: lavender, rosemary, echinacea.
Skip until year two: anything you’ve never used, anything that needs a specific harvest window you don’t understand yet, and anything expensive.
Contain these or regret it: mint and lemon balm. Both spread by runners and both will take a bed. Pots, or a bed you don’t mind giving over to them entirely.
Seed or transplant?
Both, depending on the plant.
Calendula, chamomile, and dill go straight in the ground from seed and come up readily. Buy those as seed. It’s cheap and it works.
Rosemary, lavender, and thyme are slow and fussy from seed. Buy those as plants your first year. You can learn propagation later once you know you like them.
The part nobody mentions
You will grow more than you can process.
Six calendula plants will produce flowers faster than you can pick and dry them. That’s not a problem exactly, but plan for it. Know how you’re going to dry things before the harvest is sitting on your counter wilting.
That’s a whole post of its own, and it’s the next one.
If you plant nothing else
Calendula. It comes up easily from seed, it blooms until frost if you keep cutting it, it’s the base of the most useful salve in the cabinet, and it’s pretty enough that nobody will complain about where you put it.
Start there.