Actually so did I at first...im assuming u m ean jaggedy right..?
1 you can't have any lines...outlining anything..like a block has to be a straight color..no lines around it...deep lines..
Also Saving it as a jpeg...for some reason ..doesn't work well wit it either.."Sometimes"
What i do is basically draw the wall and fill with color and then apply gradient..come back outline it in paint ..and do the same with each wall..or whatever u are working on..
Basically one object at a time..or wall at a time works for me..
Peace