I invoked The shenron, but there was only one request option. There is to ask other things to shenron?
Yes, the Dragon Balls the game gives you in the quests are Tier 1, they can only give you some kickass level 20 gear if I remember correctly, take them more like a long quest chain reward.
The real Dragon Balls are a lot harder to get (depends on your luck though) killing monsters that are marked with a Dragon Ball in your radar (the chances they have it are incredibly low, I tell you) and they give you stronger rewards, like some cool weapon, an unique powerful skill, or race transformation, or powerful gloves, or etc (I don't remember how many things you can wish for).