So to get the dwarven blackbow in dragonborn you need at least 3 gems, well the thing is you get to buy one of them, which I did, and then another is in a temple which I have.. Now the last 2 are with the bandit infront of where you put the gems to get the bow, there's suppose to be 3 bandits and the leader is suppose to have 2 of the last gems on him, but the thing is that I only have the 2 bandits there and not the leader, so I can't get the bow because there's no leader for the last 2 gems, I even deleted the Skyrim game data and installed it again and it still doesn't work. Anyone know how to help me with this??

Here's a complete list of where you can find all the gems.

From the Elder Scrolls Wiki.

Mark41 will probably be able to help so wait till he posts, I don't have the DLC's but if a quest is bugged you can try reloading an earlier save (You do make regular manual saves don't you?) and see if the quest triggers correctly.

I think updates were intended to prevent essential NPC's from getting killed but I wouldn't trust that is the case and if he has been killed somehow then a reload would be needed.

edit- or you could go follow the spoiler above and find another gem.

There's 4 gems total, you need at least 3 of them, I have 2 of them, but the last 2 are suppose to be on the reaver lord in kagrumez, but the thing is that he won't spawn, and so I cannot get the 2 gems from him, and so I can't get the dwarven black bow either.

You only need 4 gems, and there is a total of 5.

You find 2 on the people in Kagrumez
You can buy 1 from the merchant at the Silt Strider
The other 2 are in the remaining Dwemer Ruins on Solstheim
*Nchardak
*Fahlbtharz

If you have lost access to 2 of the gems, you may be able to use the run through walls glitch to run through the gate.

Hold up a flat object (like a wooden plate or platter) and sprint (or Whirlwind Sprint Shout) through it.

You can check this out also:

http://www.youtube.com/watch?v=izyP6gBgb8M

It describes precisely how you find your gems...good luck. (I am not so far yet anyway...lol)

Did you read what I wrote in the spoiler tags? It mentions 5 gems, not 4.

I said this sooo wrong, no no no, I have 3 gems and you need at least 4 and 2 of them are gone.

But thank you Mark41! The run through the gate glitch worked! I finally have my bow, thank you!

Another happy customer...lol