F(26 CAN-> US) looking for advice about moving to U.S

Hello all. I'm seeking advice and answers to my many questions about applying for a K-1 visa and moving to the U.S. I'm kind of new to Reddit so I'm sorry for the format if it's not correct. For starters, I guess a little background information is needed here. My boyfriend (M27, U.S) and I have been dating for the past 2 years and are looking into closing the distance in the next couple of years. We've looked up the various visa's and I have talked to lawyers who specialize in Visa's and immigration. Our most viable option is to get married and we're both okay with that. I do, however, have a couple of questions for those who have closed the distance or are in the process of closing the distance. My first question is when would the ideal time to apply for a K-1 visa be? I've heard that the visa process can take up to several months. Secondly, I was wondering if there were any fees for the K-1 Visa. The U.S embassy website is very vague about this. Once the whole process is over and you have obtained your K-1 Visa, are married and are living with your S/O, how long does it usually take for you to get your green card to work? Lastly, I was wondering how much money you saved before moving? Right now, I work full time and don't have much money saved up but I'm trying to aim for 15 000$ USD to sustain me until I get my green card when I move down there and I was wondering if that was enough.