As DStanley said, your numbers sound plausible, but we have no way to know what your actual expenses are so it's hard to say.
Here's how I create a budget.
First, there is no such thing as a "necessity". There are only varying degrees of "wants". When people are making a budget, they often say that things like the mortgage and the electric bill are "fixed expenses". No, they're not. You could always look for somewhere cheaper to live, etc.
That said, start your budget with the things that are hardest to change. Like taxes, debt payments, and legal obligations like your child support. If you don't have enough income for those, you're in serious trouble and need to seek professional financial advice. But let's assume you can cover them.
Then go to the next tier of "difficult to change", like rent or mortgage. (Well, mortgage is a debt, but easier to change than, say, a student loan.) Continue working down the list.
For things that are variable, like electric bills and groceries, use the average amount you're actually paying now.
Include an allowance for irregular expenses. Like, you apparently have a car. Presumably now and then the car breaks down and needs repairs. Find what the total has been for, say, the past 12 months and calculate the average per month. Similarly, you probably don't buy new clothes every week, but you do now and then. How much does that come to on average? Etc.
Go over your credit card bills and bank account and make sure you're not missing any expenses. It's easy when putting together a budget to forget things that don't come in regular bills. In my younger days, I found that I spent a lot of money in cash that I had no idea where it was going.
Then when you get to the end, compare total expenses to your income. If income is more than expenses, hooray! Decide what you will do with the difference. Pay off some debts faster? Build some savings? Invest for retirement? Etc.
If expenses are more than income, go back over the list and figure out what you can cut. If it's close, maybe you just need to make some minor adjustments, like don't eat out so often, or don't buy so many video games.
Personally, I devote most of my effort to minimizing regular expenses and very large expenses. If therer's something that I spend $100 on once a year and I can cut that to $90, I save $10 a year. But if there's something I spend $100 every week and I can but that to $90, I save $520 a year. For infrequent purchases, if I can save 5% on a toaster, big deal, what's that, maybe $1? But if I can save 5% on a house or a car, that's a very big deal, thousands of dollars.
I worked fairly hard to get a house at below-market price to keep my mortgage payments down, and I drive a used car that I bought with cash so I don't have a car payment. Where you're willing to cut back depends on your priorities. If it's very important to you to have a fancy new car, okay, that's fine, as long as you can cut other places to afford it. As long as you don't say, "I just have to have the newest and best of EVERYTHING" and you don't have the income to support that. And as I said up front, you almost certainly do not NEED a fancy new car. Maybe arguably you "need" some sort of car to get to work. But you could manage with some beat up old thing that runs, it doesn't have to be new and it doesn't have to be pretty.