Hello! I was wondering whether or not I could build and design my own Arduino if necessary? Is it feasible or is it something that would take me years of study and lots of specific materials?
Sure you can, especially if you start by copying one of the existing Arduinos. They are, of course, open source.
I assume that you have the appropriate CAD programs and experience already.
But why would you want to? There are so many in existence already and they are fairly inexpensive and work with the existing software. Are you planning to put something else on the board?
^ what part says! LOL
Seriously.. get used to what a BAREBONES/BREADBOARD Arduino requires...
Once you comfortable with that.. its fairly easy (outside of learning whatever software package you decide to use) to make your own verions in what size, shape or extra's you require.
I did the same thing/path.. played with Arduinos... learned about making my own Arduino 'compatible' circuits... and then moved to designing my own PCB's/boards (ordering from PCB board houses..etc)
Its really a liberating feeling/thing to learn.
Yes, yes you can. The ATMEGA 328P comes in several packages, from the easy to use dip on the UNO to surface mount tiny QFN's. Same goes with crystals and capacitors. If you are relatively new to this, I would recommend sticking with dips and through hole parts so you can mount them on a breadboard and also makes soldering with minimalist tools easier. You are much more likely to be successful.
Hi,
Welcome to the forum.
What exactly do you mean your own Arduino?
You can make barebones Arduinos like this;
They have no USB interface, you need a different programming system to program them.
Can you tell us your electronics, programming, Arduino, hardware experience?
Tom... 
Using 328 is easy.
If you can design your own boards and you have an Atmel programmer, you can easily make any Arduino board. You have to use ISP pins then. Usually the USB is hardest part to build. Just check where parts you need are connected and make your board similar.
I think it is not even necessary to use Atmel programmer, but I have so I havn't studied that.
Edit: But of course others have already told you this.
LMI1:
I think it is not even necessary to use Atmel programmer
An ISP programmer is necessary if you want to set fuses, burn bootloader, or upload to the microcontroller without using a serial to USB adapter (Sketch > Upload Using Programmer). It's possible to use another Arduino configured as an "Arduino as ISP" for this purpose or dedicated programmers such as the USBasp are available cheap on eBay.
You can buy ATmega328P chips that already have the bootloader installed and in this case you will not need an ISP programmer.
Suggest you stick with Anduino Pro Mini. ~$3.00.
You would need one FTDI to program them. ~$3.00.
There is also the Arduino Nano.
.
The Arduino isn't a board, really - it's a development environment with a very helpful community, originally based around ATMEL devices and boards built using them , but it now supports many other platforms.
All the Arduino boards have open-source hardware designs, both as Eagle schematics and PCB designs, so you can easily use them as a starting point for a product of your own, using these designs as a base.
Even for small professional use, it's a very versatile, quick and viable approach.
Allan
allanhurst:
The Arduino isn't a board, really - it's a development environment with a very helpful community, originally based around ATMEL devices and boards built using them , but it now supports many other platforms.All the Arduino boards have open-source hardware designs, both as Eagle schematics and PCB designs, so you can easily use them as a starting point for a product of your own, using these designs as a base.
Even for small professional use, it's a very versatile, quick and viable approach.
Allan
Yes.
And in Arduino boards the majority of parts is for USB, if you can live without that, the rest is easy to copy.
As the others said, it may depend a bit on how technical you are, but it's certainly possible :).
I started playing around with arduino 2-3 years ago. Then moved on using arduino on stm32 boards, since they are also cheap, and more powerful.
Then slowly started going beyond the arduino framework in programming (learning the inner workings of the microcontrollers, programming using the manufacterers toolchain), and later on started experimenting with soldering more powerful stm32 chips on the boards i had. And then started to design my own boards, and last week i just sent my 4th iteration of the boards i'm making to a boardhouse in china to have them produced :).
Of course, it is quite a journey, one you won't make in a few weeks, but it's fun. And like all projects, take it step by step. The breadboard examples above are a great idea. Also like i started, modifying existing boards with pin compatible microcontrollers is a fun way to go further, and then choose a pcb cad package (i'm very happy with KiCad), and start learning how that works :).