Unless you hire a credit repair agency to help you remove any negative remarks on your credit report then there's no legit way of raising your credit score as quickly as 30 days.
However you can begin to raise your credit score by calling up any debt collectors that you know you can pay off and ask the debt collector whether they will remove the negative remark from your credit report and mark the balance as paid in full if you agree to pay the collection agency in full.
Some will remove the negative remarks while some won't. If the debt collector won't agree to remove the negative remarks and mark your account as paid in full on your credit report then don't agree to pay them anything.
Move on to the next collection agency and ask them the same thing and if they will remove the negative remarks then pay them off and if they do remove the negative remarks then it will help boost your credit score a little bit over time.
If you currently have bad credit you can get a secured credit card through Capital One or another credit card company where you use the credit card like any other credit card and pay the monthly bill but you place a deposit of $200.00 or more which will be your credit limit and if you're responsible paying back the credit card you'll eventually get the deposit back plus it will boost your credit score overtime.
Also if you have any current loans open then keep the loans open and in good standing because the longer you have the credit going and the loan open with good payments the better it looks for your credit score and credit rating and it shows other lenders that you're a good risk for credit and that you're responsible when taking out loans and paying those loans back.
A credit score might improve a little bit over 30 days but there's no way to actually raise your credit score too much in just 30 days.
It's gonna take time to rebuild your credit or to increase your credit score.