The first sentence is for the most part correct, but you may want to add in a comma. Also, generally abbreviations (i.e. Sep for September) have a period after them. For example:
"You're invited to my birthday party, hosted in the DNA Asian night club on Saturday, Sept. 4th."
In the second sentence, you should say "The party starts at 9:30pm." The party starting is not a continuous thing, so it happens 'at' an exact time.
I don't think you need to include "for the reference of..." in the next part. I recommend saying:
"The night club has 2 dance floors,"
Floors is plural, because there are two (2) of them.
"professional DJs, and drinks of your choice."
Professional describes the DJs.
"I have reserved a couple of tables on that night in the club, so if you don't want to dance with the public, you can still sit down and enjoy your drinks."
Note in the next part I added 'a' before 'couple', and removed 'people' after public. Though the second part (public people) is correct, the phrasing is awkward.
"If you like to dance with pop hits, great!"
Pop (i.e. popular) describes the hits, rather than the hits describing the pop.
"There will be the group of birthday people and also other people who come to the night club regularly."
I'm not sure how to explain what I changed in this sentence. Maybe someone else can help to explain it?
"The admission to the night club for people on my birthday guest list will be $10."
I rearranged the middle of the sentence, although again I'm not sure how to explain why. I removed the phrase 'to the night club' at the end of the sentence, because you already stated the same thing at the beginning.
"You will also pay for the drinks at the counter if you need a variety."
Again, I removed 'of drinks' from the end of the sentence because it was already stated at the beginning. I do have a question about the sentence though, because it may be confusing. Are the drinks only paid for if you need a variety? If 'you' need to pay for all of the drinks, need for variety or not, I recommend saying the following instead.
"You will also pay for drinks at the counter, where there is a variety available."
"So friends, come out on Saturday and let's have a fun night."
I don't think you needed the first comma, though I'm not completely sure. Also, I recommend spelling out Saturday. I don't think you need to say "with everyone else" at the end, either.
dj's -> DJs
I think that DJs is the proper way to write the plural. dj's implies something belonging to the dj.
I'm new to this forum, but I'm a native English speaker. I hope I helped!