I cant get damn key fragment

You're more likely to get a key fragment if you win normal/rank games on the rift. They're supposed to drop in ARAM but its currently bugged. Just keep playing games. I have a few chests but only a key fragment for several days now even with the wins. The drop chance decreases as you get them too as well. So all you can really do is just play or spend rp on keys.

Your welcome. Riot is also announced they are fixing the drops in ARAM in 6.7 Patch. So check the post on the home page if you haven't already.