Over the years, most of us have come up with some steps you use to start building a setup. I'd like the members add to this list of ideas. This is not the details of your setup, unless you wish to post those details to share, of course!
1) Try to " ride along " with a front runner and look at the speeds of their shift points. That will help get you in the ballpark of there gear ratio. As of 2022 our leagues mod only allows changes to the final gear ration and not each gear. That means you could pick even 5th or 6th gear to figure out the gearing.
2) Don't use top speeds to determine too much. You don't know their fuel load, their boost settings, if they used DRS , or even if they used a temp boost on the straight.
3) Start your setup to optimize the corners that connect long fast sections. That may mean you had enough downforce limit your top speed.
4) Set the front and rear anti-roll bars to reduce front tire wear to a reasonable amount so you don't have to pit for tires more often than most of the field.
5) Drive with the above basic settings until you are sure it's the setup that is limiting your lap time and not mistakes you are making. Resist the desire to start changing things to make up for your driving errors.
6) Save the basic setup and then as you make changes, save it as a new name so you can always get back to square one. Maybe this setup is faster than your latest one as you where going down the wrong path trying to improve it.