Where are you located?
I would probably advise against changing the weight classes unless you go over/under by formula. Example: <198, >198 is a common break up for the mens division.
You typically will have a mens open division by weight class with a best lifter award based on formula, and the rest of the divisions by formula utilizing categories (Womens, Masters, teen, Junior, Novice, whatever.)
You should probably consider a best lifter award for these categories as well. Obviously, fewer categories/divisions is better. Especially at your first competition.
Wilks formula is the standard. A simple google search is all it takes to find a chart. It is easy to utilize.
We direct several meets a year, so if you want more specific advice, feel free to pm me. We can correspond via email.