Most herbs are easily grown from seed. Most are also annuals and so August is a little late to start them, but doable. I would not mix herbs in the same pot as the more vigorous will overwhelm the others. Starting seeds in the summer will require care to keep the soil moist until after germination, either by covering with clear plastic or watering multiple times per day. Al

'Most are annual' is not completely accurate. Many of the most useful and popular are perennial eg sage, thyme, mint, rosemary, bay, lavender, oregano and chives. I cannot comment on the suitability of August for sowing because I do not know your climate but I would suggest you look up each herb you want to grow since they do not all require the same conditions. Some such as Parsley, coriander, and dill resent transplanting so are best sown straight into their final homes.

There is a Herbs Forum here on Garden Web where you will find several experienced herb growers to help you.

I would not suggest starting Rosemary or Oregano from seed. You may be able to find someone in your area that could give you a cutting or plants. It is suggested that herbs should be fall planted for our area but then not not all annuals, such as Basil or dill. Mint needs to be by itself as it as well as Oregano love to wander. Some Sages are annuals, bi-annuals but some will last for many many years once established. Bay trees do okay in our area. Lemongrass does not like a freeze but here if we expect cold weather we can take cuttings and store in our ref's for save keeping for when our weather warms back up for the summer.