Crappy helmet could be the first issue. If you are serious about welding even for home or farm repairs, try spending at least $100 on a decent one to start.
As for shade, everyone's eyes are different and it can depend on what you are doing. Since I put in a pair of cheaters, I have found I needed to move my shade up from 10 to 11 or i would start seeing spots after a few minutes of welding. Sometimes that makes it harder to see, but a halogen worklight on the weld area will do a lot to fix that. Find what works for you on shade. If you try 11 and can't see diddly, then try 10. Still too dark? Try 9. When you get done welding and start seeing spots, you know you went too low, so bump it up one at least. Then if it is hard to see, try extra light like the halogen i mentioned. It reduces the contrast between the super bright arc and the surrounding area, making it easier to see what is going on.