What's the usual credit limit I can get approved for with a bad credit score?

The credit limit you can get with a bad score depends on the type of card you wish to get, the company that issues it, and your overall credit standing. 

Most secured credit cards require a refundable security deposit of at least $200 that will serve as your credit line. So for example, if you place a $300 deposit, your credit limit will also be $300. 

With an unsecured credit card for bad credit, like the Credit One Bank Credit Card, the credit line that you will ultimately get approved for is hard to predict. Credit One will make that determination based on your income, debts, and the exact nature of your credit history.

I would say a 600 or better because anything under is considered bad credit

Depending on the lender and the kind of credit product you are looking for, the credit limit you can be approved for with a poor credit score will change. In general, those with bad credit will have lower credit limits than people with strong credit. It's possible that you'll be given a credit limit between a few hundred and a few thousand dollars, but it's also possible that you won't be given any credit at all. It's crucial to remember that having a low credit score might lead to increased interest rates and costs.