I have a 40 gallon. I'm looking for pretty, cheap plants. I'm not sure on my lighting but I don't think I have very high lighting, so I guess suggestions would need to be for low lighting.

I'm partial to grass-like plants. Which plants do people usually use to make that grass-like effect?

Most of the "grass like" kinds need moderate to high lighting to thrive. Dwarf hairgrass could be worth a try though. I think it's more skewed towards minimum lighting...