Pretty wild, I was going to make a post about stardust today. Since I saw this post, I'll just add it to this thread. Check this out.
I'm now a level 19 (almost 20). I've been noticing that Stardust at this very moment is pointless until end game. For example, if you spend stardust on a 200 CP Pokemon to get him to 450 CP, then head out and catch a pokemon that has 450 CP, you just wasted all that stardust on that one particular Pokemon. I've found that as I level higher the CP meters of the Pokemon caught drastically get higher. As an additional example, is that I was wandering around catching Pokemon and snagged a Paras with a CP of 410.
Here is what I'm getting at, if you dedicate time to play - you shouldn't spend any Stardust till you hit level 40 and are catching Pokemon at their full potential. Then when you get there you'll have like 500,000 (example) stardust to push them to MAX and then you'll have all the end game strong Pokemon.
Let me know what you think of this, but I'm truly thinking that early game stardust is absolutely pointless.