The amount luck you need really depends on what level of artifact and # of property you want on that eventual clean item drop.
Yes you might get more clean item with lower luck but on the flip side is that even high level artifact drop (greater+) will normally have crappy mods.... When I get a Greater+ artifact, I do not want crappy 5-6 mods when it should have been high intensity with high # of properties.
Nothing sucks more to get a a high level clean arti drop and get shafted by low property count along with low intensity. With higher luck, the lower the chance you will get a clean item. But if you do get that clean drop, you will not run into the lower intensity\low property count item issue as often.
You have to determine the amount of luck that works best for you..... If I want decent pieces then I tend to target my luck to where I can find clean lesser artifact on a regular basis with occasional chance to get a high end piece (1700-2000). If I want to go for broke, I will go with 3k luck and cross my fingers.
1000 luck range will give you a good balance of useable items (imbue-able \ good high intensity Major magic item to lesser artifact).
With 1000 luck if you do have an old account, you can hit that statue and allow you to try for the higher end item for couple hours a day.....
Don't believe what other people tell you, test it out yourself and find your own luck zone.....