This must be one of the most commonly asked questions by new cosplayers. I see posts about this every day on the forums I’m active at. They often include a short statistical description and an image. The thing is: this doesn’t help at all.
At its core, cosplay is about dressing up as a fictional character. What you look like out of cosplay does not matter at all. That is the beauty of it; no matter what you look like, there is always a way to make you look like someone else. The right makeup goes a long way. You can use corsets, padding, binding, prosthetics, wigs, lenses, and various other techniques to change how you look or even your perceived gender. So no, what you look like is irrelevant; all that matters is your creativity and your motivation.
People often say that you should start small, I say screw that! If you have time and motivation, then find a cosplay you really want to create, and dive head first. If you don’t know how to make some part of your cosplay, then take your time and learn, the skill will probably be useful in the future. If something about the cosplay doesn’t come out as you imagined it, then redo it until it does.
But how do you find a character to cosplay? This is a process that cannot be stressed. You will spend a lot of time with the character, and you need to be sure that you really want to cosplay it. No one can tell you who to cosplay. If you don’t know who to cosplay, then don’t force it, let it take its time and a character will come to you.
As a side note:
This is not a post about the traditional argument for “You can cosplay whoever you want”. While it is true, I would rather argue that “Anyone can make an accurate cosplay of any character; it is just a matter of creativity and motivation”.