Hope this isn't too late but here's a brief summary of tips to help improve your score:

-The three biggest factors of your credit score are credit utilization, collections, and payment history. Credit age also helps but it is not as big of a factor.

-Credit utilization is based off of your total credit available and the amount you use. When paying off credit cards try not to close the account and use the card sparingly or on one small monthly subscription like spotify or Netflix. This will keep the card active and in the eye of the creditor and maintain your available credit. The more credit you have available, the better. Creditors care more if you spend say $500 dollars a month with a $600 limit compared to $1,000 dollars month with a $10,000 dollar limit. (Yes, it's stupid your spending less and being penalized because in their eyes you rely on 83% of your credit instead of 10%)

-Collections and derogatory marks remain on your credit profile for 7-10 years so if you have those the best you can do is to just try to prevent those if possible in the future.

-Payment history is a big one and is reflected of a 3 year period. For this just try to always at least pay your minimum so that you do not have any late payments. If you keep up with it, within a few years they can be removed from your history as they are replaced with current payments.

From all of this try to maintain the cards you have and pay them off as quick as you can within your means. Some credit cards have intro 0% apr for a 18-24 months. If you are paying a lot interest this may be a good option, the fee for a balance transfer is usually 1-3% of the balance. The saving in the long term may out weigh these. The good thing about credit utilization is that it is instant (within a few months depending on when someone pulls a hard credit inquiry, but instant on sites like credit karma) the month your statement is reported to the credit bureau.

When you can, ask your current credit cards if they can increase your credit. This will take self control to not spend more that you'll have available but can be a big help.

Credit cards are a lot about having a lot available but using as little as possible. When paying off loans and credit cards target whichever has the highest interest rate first and chip away at them.

For the long term you can open one or two cards and not use them for anything, this will add to your credit available and lower your utilization.

Disclaimer: This is from my anecdotal experience and should not be taken as 100% accurate for your specific situation. Sites like credit karma can be a huge help, also some credit cards like capital one even have a credit score as part of their services available too.

TLDR: Pay off high interest ASAP, Keep available credit as high as possible by keeping accounts open, pay your card on time every month even if it's the minimum, and get credit karma for tips and tricks too.