Help in achieving a credit boost?

I had maxed out 2 credit cards one 1000 and the other 2500. These accounts are both closed. I just paid off the 1000 balance in full but my credit only went up a few points. I’m in a rough spot because I need good credit to get an apartment but my credit is at 552 and 530. How can I get my credit up to at least 650 relatively soon? Is the secret in just paying off my balance ASAP?