It was very interesting to do this tutorial. I learned a lot of things! Even if it's only pennies, it feels exciting
>> A little bit about what I did and a question about when to stop <<
First, I made a $50 deposit into my PopAds account (I don't know why, but they gave me $60)
I've played a lot with different geos. First, I started with all the ones my AM sent me.
Only one of them had a minimum profit and other one a little bit lost. So I made separate campaigns for those two geos. The one that was profitable, in the separate campaign never worked. The one that with little profit, didn't work either.
Then I tried other geos that weren't on the list (8 more) with separate campaigns. None of them have worked so far, but I still have 2 active campaigns for two of those geos
Geo 1 (Tier 1): 3 campaigns with different budget, from 0.0002 (the only one with profit) 0.0004 and 0.0008
Cost: $5.34
With. Value: $4.38
Profit: -0.96
Total prints: 7,773
Conversions: 73
Geo 2 (tier 3): 1 Campaign with 0.0002 budget
Cost: $1.06
With. Value: $0.88
Total prints: 5,317
Conversions: 44
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So, here comes my question
When you're doing campaigns with so little money ($2.5 - $3 each), how do you know when you have enough data to stop or continue? Maybe it's obvious, but I don't see it so clearly.
For example, I've those two campaigns. As you can see, in one I've invested $5.34, although it doesn't generate a big loss, the profit goes up and down (8 hours ago it was -$0.20 , then -$1.38 and now it's -$0.96, yesterday was +$0.20)
I mean, I'm losing $0.96, but that's a ridiculously small amount compared to what I've tried with that geo ... but at some point I have to stop ... or invest more? or keep playing and losing a bit? 
I know, I'm analyzing pennies, it's no big deal. I also know that you don't have a magic wand to know what will work or not
. But what should I take into consideration with my pennies? take this campaign as over?
PD: In the end I spent $32.24 and earned $16.81... Well, considering that I received an extra $10 in my deposit. I only spent $22.24 out of my pocket and earned $16.81: -$5.43 lost. Incredibly good for the experience.
Thank you!
Agree with @matuloo that these are great results!
And you're right - it's pennies - and that's what's so amazing about these campaigns! You can learn optimization for so much less money than if you were promoting an offer that requires spending $5 or $10 or more to get each conversion.
So - have fun with it and test different things! 
It's normal to get less traffic and lower-quality traffic when you're targeting a single geo, vs. multiple geos.
One thing you can do: Take that original multi-geo campaign, and cut gradually - starting with bigger geos that are in loss by < -30% ROI, say. Then cut placements that are in loss by say 3x payout (I know different geos have different payout amounts - maybe take the average of your top 3 geos sending the most volume - not counting the geos you've already cut).
Note: The 3x payout in loss should be sustained AFTER you've cut the bigger geos that are in loss by < -30% ROI, not based on stats from the beginning of your campaign. Because stats since the beginning of your campaign will include the "big bad geos" - you can't "fault" your placements if a geo is performing badly overall. 
When you reach the point where you've gone a day or more without having any placements to cut, and the campaign is still in red, try increasing the bid by 30-50% for a couple days to see if you get better ROI.
Or, if after cutting some geos and placements, the campaign is profitable, you can still test a higher bid. If your get worse results, revert to the previous bid.
Or, leave the profitable campaign alone, duplicate it and increase the bid for the new campaign. That way you don't risk "messing up" the original campaign.
And of course, you can continue doing what you've been doing: Run separate campaigns for each geo, and cut placements and test bids for each campaign.
Hope that helps!
Amy