The first step in formulating a good recipe is to look at lots of recipes that other people have used. You can find lots of recipes online. Look at many different ones for the style you are interested in. This will give you an idea what kind of ingredients people are using, what quantities are typical, etc. You'll generally find that for any given style, some ingredients are universal, while others are optional, so by seeing what other people have done, you'll get an idea what the options are when it comes to making up your own version.
Then, formulate the recipe using brewing software (I use Beer Smith) or an online calculator, so you can work out the alcohol level and IBU. Post it here, and someone will be sure to give feedback on it.