Welcome buddy.
Nice project selection and good time to start working on them.
If you want to develop from scratch then things you need to consider.
1. You need a library to read PWM values from RC receiver(you can also build one). If receiver has PPM output then your work is easy and libraries are available and I have a custom library built for atmega328p(atmel studio compatible not arduino IDE compatible).
-->you have input at this step.
2. You may need a library to communicate with MPU6050 accelerometer + gyroscope. I do not suggest to write a library for this as it may consume so much time because you may have to study complementary filter or kalman filter or extended kalman filter which are filtering algorithms to determine the tilt angles and angular velocity.
-->you also know quadcopter state at this point.
3. Now you can concentrate on writing your main application and you have to understand the motor mixing in quadcopter(you can ping me I worked on it sometime back).
4. Now you need to understand the PID control system looping mechanisms and mix the outputs and outputs must be sent to motors accordingly.
You can rather build a brushed version of the same, a tiny quadcopter lets say 100mm which wil cut down your repair cost.
However I do not recommend you to start your work from scratch as it is very much time taking process and needs to be funded because there may be lot of crashes and all.
You can have a look at his work. This is very basic yet very good to get you started.
http://www.brokking.net/ He has everything you need to get you started from scratch to complete your copter. The code is very well documented(I felt it don't know about you). He posted his entire work in step by step procedure on youtube
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You can then study the open source MULTIWII project which I believe is the first ever open source and many other flight controlling algorithm are emerged from it.
Cleanflight, betaflight are also available as open source and these are also well documented.
There is ardupilot(APM) which is open source and very well documented. It has many functionalities you can ever imagine. This is the best open source flight controller.