How many days should i apply for on my tourist/private visit visa?

Hello everyone!
I am planning on visiting my boyfriend in Turkey and he will host me as well as provide bank statements to my embassy.
I am confused about how many days to apply for my visa. I have just completed my studies, so obviously I have no income. I do not want my embassy to deny me a visa, because i really wanted to spend a lot of time in Turkey this year.

I asked the embassy if i could apply for 6 months but they said probably not, but to just apply anyway.
i really do not want to have my visa application denied. My boyfriend can afford to host me and the bank statements will prove it. I just want to know how many days/ months would be considered ok esp for an African, with our embassies being so strict  

Is it also possible to extend my stay from there by getting a residence permit or something?

Ps. I am not a first time visitor to turkey, I was there for 2 months last year.

I appreciate your comments and advice.

Thanks