Answer: Based on your description I am not certain what type of lilies (Lilium) you have, however regardless of the specific type you would not need to separate them at planting time.
If they are standing upright and blooming now, they should not need staking. The only lilies that seem to need staking are the very tall types, in the four foot range and taller. If they are blooming now, that is all the height they will have, they will not grow taller than they are right now.
Without knowing which kind of lilies they are it is a bit difficult to suggest specific spacing, but 18 inches apart measuring from the center of the pot to the next would be a start. This will allow some space for the bulbs to multiply and form a nice clump over several years before you eventually do need to lift and divide them.
Lilies generally need full sun all day long or for at least half a day. It would be better to put them in all morning sun rather than afternoon-only sun if that is possible. The reason is that afternoon sun is very intense and hot and can stress the plants in mid summer.
Lilies also do best in a soil that is well drained, so do not plant them in a low spot. Enjoy your lilies!
ps If you have more questions, please be sure to put your state or zip code in the question form. That way we can tell what geographic area you are in and can give you better advice. Thanks!
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