I am currently learning stm32, I have very little coding background, only some arduino. What is the best device to start learning on? I currently own a neucleo-f4 and must learn to program a stm32f303 for my project. Based on the videos on the STM32 website (stm32 F7, L4, L4+, and GO) which one would be best for me to watch and should I consider buying a new stm32 for learning purposes? Thanks.
The STM32F3DISCOVERY is a low cost board intended to introduce the features of the STM32F303. It has an on-board STLINK debugger. The Atollic TrueSTUDIO toolchain is free for STM32 users, as is the System Workbench for STM32 (SW4STM32). Both are good choices for a toolchain.
I believe your best start would be to use the STM32F3DISCOVERY board (same chip as your final project) to start learning how to blink LED's and read buttons. Then try to use the various peripherals your project will require. The Discovery boards have some additional peripherals connected on them that the nucleo boards usually don't have.
You could use the board you already have for some of the basics of learning how to use STM32 parts in general; however, if the final project will be a STM32F303 and you're willing to invest in a development board then why not use the same STM32 to learn as the final project will use?
ST has a software package called STM32CubeMX which can help create a C language framework and handle most of the basic settings of the STM32: things like internal RC, external crystal, or external clock and so on.
Start coding and make something happen. If it doesn't then you'll have an example of exactly what isn't working and can either debug it yourself or ask for help.