When using an ATV disc, the heavier the better, and anything you buy will probably not be heavy enough. Do not think for a minute you will get "tractor-like" results using an ATV disc. If you can burn the field and get rid of litter and plants, you will get better results.
We have used a King Kutter ATV disc for the past several years, purchased at Tractor Supply which weighs about 300 pounds. In perfect soil conditions it does a fair job, but only after we have put a hundred pounds or more of extra weight on it. And it takes several passes in various directions to get those fair results. We added weight to the disc to the point where my 500 Arctic Cat could not pull it and it was still only doing a fair job up to that point.
Something to remember, you will get better soil disturbance when turning. Often times we have disced larger fields by simply making a series of circles over the entire area, then coming back and straight discing to kind of neaten things up.
Best of luck, an ATV disc is better than nothing and with a lot of time and work, you will get a soil surface that works pretty well.
“There are two spiritual dangers in not owning a farm. One is the danger of supposing that breakfast comes from the grocery, and the other that heat comes from the furnace.”