USB miners is like the dumbest decision you'll ever make... They profit you literally nothing, especially with the difficulty rising quickly.
Dunno, they make amazing lottery miners. They have a different purpose than let say a S5. They fill a different niche and just like any other hardware, some sticks are great (sidehack stick 8-23GH/s+) some sticks are horrible choices (nano, 400MH/s, etc whatever).
isn't better at this point to try your luck with the best faucets freebtcio, which give you a lottery, which is far easy and it's almost free and no electricity cost?
I don't know, do you stand to win 25BTC at one in a millions odd every day all year?
I kind of doubt some faucet operator would make enough money to come up with such a big prize, and if there is indeed such a prize that get accumulated, i would doubt it get handed off often.
That would also not teach you how mining BTC work. I think a USB stick is great to get the hang of it, since when you're getting your tiny payouts on the stick, going to real miners is actually a easier endeavor.