Am I considered to be immodest (mutabarrijah) for not wearing the hijab and applying a lot of makeup, or is God merciful to those who try to develop gradually, and are my prayers permissible and accepted?

You are on the right path, and your acts of worship and supplications are accepted. Allah’s mercy is vast, and He does not equate the obedient with the disobedient. Continue with your prayers and abandoning musical instruments, and utilize the good within you. Do not let Satan corrupt your relationship with Allah. Abandon makeup and wearing tight or eye-catching clothes, out of obedience to Allah. This might be difficult at first, but you will find the sweetness of obedience. Beware of belittling sins, seek Allah’s help, associate with righteous women, and adhere to dhikr (remembrance of Allah) and du’a (supplication).