Answer: Unfortunately, your plants will probably quickly become too crowded in that pot, even if you only grow one of each kind. These herbs are also sunlovers, and need as much light as possible when grown indoors. Finally, your pot will hold moisture longer than an ordinary unglazed pot would, so take care not to overwater the plants. If the pot does not have a drainage hole in the bottom, you might consider instead using it as a cachepot -- plant the herbs in a terra cotta pot and set that inside the decorative pot. This method allows you to rotate the herbs in addition to helping avoid overwatering.
Chives should grow to form a clump, with new growth starting from the base. You may trim the leaves whenever you like, some gardeners prefer to give the clump an occasional crew cut, others will trim a leaf here and a leaf there. Trimming it helps it gorw into a thicker clump faaster.
Cilantro is a cool weather grower, and should grow quickly because it is an annual and consequently tried to grow and make seed fast. You may trim it, but do not expect too many cuttings from one plant.
Oregano should be allowed to grow to about four inches, then pinched or trimmed lightly to encourage it to branch. Each trimming will cause it to branch again, so frequent use for cooking is fine. This plant tends to grow leggy indoors, and trimming will help counter that.
Since your plant is not growing much, I suspect it may be too crowded or it may need more light or it may need less water. This plant does not need as much water as the other three plants enjoy and it really prefers a lot of sun, outdoors it is planted in full sun all day.
Basil usually does well in a sunny window and will grow erect unless pinched to encourage bushiness. You may pinch and trim as needed to use it, beginning at about the third leaves. This is not a long lived plant (it is also an annual) so you may find the plant becomes exhausted and needs to be replaced every few months.
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