I've only cosplayed 4 times and 3 of them have been actually decent.
First off, shop around for cheap cosplay outfits if you're not confident about making your own. I certainly aren't, I can make accessories like when I cosplayed Fluttershy I made her wings and ears but everything else was shop bought and slung together, still looked pretty good. I know a few good sites. I've been fairly lucky and bought from sites that look dodgy and it's been okay.
You seem pretty lucky, you could probably pull off most looks. If you want to look good and take it seriously, play to your strengths. Go for characters with a similar build to you, or even a character you would feel comfortable wearing their clothes. There's no reason you couldn't pull off a bigger character than yourself as long as it's not a ridiculous difference.
If you just want to have a laugh then you could go for anything as long as you feel comfortable.
Don't ever cosplay something you're not comfortable wearing. I have much more fun in a good cosplay because people want to interact with you more and respond more positively.
I would NEVER cosplay a barely naked woman. I don't have the figure to do so, and I don't want people seeing all my wobbly bits when I could look much better in another outfit.
I have cosplayed a slim character with fairly small boobs when I'm the complete opposite but loads of people said I looked good and cute so I think as long as the outfit is good, you can look and feel good.
That's just my advice, cosplay doesn't have any rules, so just enjoy yourself

You'll be surprised what you can pull off and how good you'll look so don't be afraid to be adventurous.
Most of all, be confident!
For reference, my cosplays:
I'll add more later, they're all on my Facebook which is down at the minute ;_;