Ultra Wide Lens Consultation?

I use Nikon D5100.
I'm not planning to spend too much on an ultra wide lens. I'm just going to practice photography with these lenses. After I got experienced enough, I would switch to a more expensive one.
By now, neither the quality nor the sharpness of the final photo really matters. Low price and high FOV is important at the moment.
What would you suggest?

Sigma's 10-20

Personally i use a tamron 10-24mm