I wanna implement Fourier transform myself
what exactly is your goal? learn about juce::DPS::FFT or making a bass booster? just asking because there are probably easier ways to make a bass booster than to transform the whole signal into the frequency domain. you could for example just use a lowpass filter to get a seperate signal only consisting of bass and then apply stuff to that like gain boosts, saturation, compression or envelope shaping, then mix that back to the remaining signal. consider that FFT also introduces a lot of latency, so you should only really use it if you need it
I just wanna make something that enables me to implement Fourier transform myself and not just for school project but can be used in the future.
Do you have any ideas?
So is your main goal to implement an FFT engine yourself or find a cool application for an FFT?
Implementing an FFT from scratch is likely a fun task but be aware that the result also very likely is nothing you want to use in real-world projects. There are so many so good implementations out there and years have been spent optimizing them to a max that it is a pure waste of CPU trying to build your own FFT instead of using the highly optimized implementations out there – except you are planing to get very deep into the FFT game and also spend month into this topic to come up with a really competitive implementation 
If it’s more about FFT usage, I always liked convolution stuff the most, you can build a lot of nice things on top of an efficient convolution and there are many options to play around with and a lot of exciting DSP math theory to dive into 
Regarding a Bass Booster, are you thinking about a simple FFT based FIR filter boosting the bass frequencies or something more fancy?
If you want to implement an FFT, I would suggest you start with a little EQ that shows all the bins of the FFT. You can then add features to adjust bin frequencies and transform back to hear how it sounds. It’s good to understand how an FFT works and what the various limitations are.
What do your mean?
And I do want to make a cool application, but I also need to implement FFT myself because it’s my school project
so make equalizer first? How?