hmm- with the exception of things like pineapple sage (which I've seen survive light frost up in z6) that are naturally tropical, I don't think you'll have any trouble with any herbs - we plant out the moment the overnight temps start hitting 40.

how big a pot? depends - the bigger the pot, the more herbs you can grow in it - all the mediterranian herbs (oregano, lavendar, rosemary, thymes, sages) can survive droughts and poor soil, wheras things like the mints 'need' plenty of water - my mom has two 5 gallon pots for her herbs, and seems to do well with everything but the basil, which seems to like natural dirt (the small-leafed thai and purple basils don't have this problem)

I've had the most luck at the extremes: either put each plant in its own pot, and repot as it grows; or plant all into a half-barrel or trough.

Herbs grow a lot bigger than most people think. One mature parsley plant just might squeeze into your oven. A mature basil wouldn't have a hope of squeezing into such a small space.

Potted plants are usually stunted, so my advice is to go as big as you can, and to plant one plant into each. Those multi-herb things you see at gardening centres are great as gifts, but I regard them as very temporary arrangements. Best to give each plant its own home, and its ideal conditions. With combinations, one usually out-competes the others, and you can't please everybody with regard to sun, water, nutrients etc.

To me, a pot 30cm in diameter is a fairly small pot.

Are you starting with seeds, cuttings or starter plants?

Several herb seeds will NOT germinate unless kept at 70 degrees or above (lavender, rosemary).

Cuttings are very choosy about moisture levels; too dry and they die and too wet and they rot.

Small start-up plants are the easiest. Be sure to increase pot size regularly or your plant will be stunted. I wouldn't recommend going from a tiny pot straight up to a huge one; double pot size each time you repot until you reach the maximum size pot that you plan to use.

Most herbs are fine and happier with the outdoors as long as you don't get a frost. Move the tender herbs, such as basil or lemon verbenia, into the hot house if you expect a frost but otherwise leave them outdoors. Again...you'll want to hot house seeds or cuttings for regulation of temps and moisture, but the plants would prefer the outdoors.

thank you guys