Yeah, its harsh to fill all the boxes, but since it is possible to clone that many items at one time I put clone up to 420 at once. The easiest way, the way I do it, is to get a few boxes full of Ditto. They are practically useless in this game otherwise. (The defense is horrible, they die before you can even use Transform, unless you are battling a wild pokemon around level 2-10, and your above 30... lol) I captured about 5 Ditto for this experement, cloned them 6 times, getting a full box of 30 Ditto.
Now right there is 30 items. Along your adventure in the game, I'm sure you took a good time catching some Pokemon for your Dex right? Well, stuff them all together, make your boxes packed full, so it is easier/faster to clone. (If you've done that you'll know what I mean)
Example: I myself use 10 boxes. Each packed with 30 Pokemon.
10 (Boxes) x 30 (Pokemon per. box) = 300 (Items, can be cloned)
So I would follow my instructions. My ending result would be 300 Items, cloned.
Now the best part. Keep reading the instructions, and do the "Continous Glitch." that 300 Items, becomes 600 Items within minutes. You can do this over and over.
300, 600, 900, 1200, 1500.... and so on. (This is for my example formula)
Thats just using 10 boxes, out of the 14.
You can still use lower amounts of boxes and be FINE. The multiplication of items with this glitch is great.
Very useful for you D/P players, who Import your pokemon from Emerald to Diamond or Pearl. Why you ask? Because you can send those Pokemon over with GOOD Items, duh! Masterballs, Rare Candys, TM's...etc. Need a certain stone? Hell just send one over, you can get hundreds of them.
Best part of all of this, no effect on gameplay, AT ALL ;)