I understand that you are in a difficult situation regarding your boyfriend and the money you spent on him. It is important to note that as adults, both you and your boyfriend have the freedom to decide whether or not to get married, and no one can be forced into it.
Unfortunately, spending money on your boyfriend does not give you the right to compel him to marry you. Therefore, filing a complaint or FIR will not be effective in this situation.
However, if your boyfriend obtained the money from you through fraudulent means or false promises of marriage, he may have committed the crime of cheating under section 420 of the Indian Penal Code. In this case, you can file a FIR against him and collect evidence to prove that he obtained the money through deceitful means.
It is important to collect evidence such as proof of money transfer or any other evidence that shows that you spent the money for his benefit. Additionally, evidence of false promises of marriage can also be crucial in proving that your boyfriend had an intention to deceive you when he took money from you.
Such evidence can include text messages, emails, or any other form of communication in which he promised to marry you in exchange for the money. It can establish that you had a legitimate expectation that he would fulfill his promise of marriage and that he took advantage of this expectation to cheat you.