That takes care of your existing credit accounts. To help establish positive credit history, you might contemplate opening new credit accounts in various categories. Showing that you can handle fixed payments as well as credit cards is a plus in the long term. An installment loan for furniture, an auto or a personal loan will round out your credit profile. You might also consider a secured credit card (make sure the issuer reports to the major credit bureaus) if you do not qualify for other types of new credit. Lastly, apply for credit only if you need it and if you can afford new payments. Credit applications generate inquiries on your credit report, which could ding your score in the short term.
Your goal with a balance transfer should be to get out of debt. If you start spending on the credit card, there is a real risk that you will end up in more debt. Additionally, you could end up being charged interest on your purchase balances. If your credit card has a 0% balance transfer rate but does not have a 0% promotional rate on purchases, you would end up being charged interest on your purchases right away, until your entire balance (including the balance transfer) is paid in full. In other words, you lose the grace period on your purchases so long as you have a balance transfer in place.