The first antminer usb stick really was 300 mega, and if plugged into a raspberry pi it could equal the output of an average gpu. That was good in 2013, but not so good now.  Look up bitcoincharts, and find a link to some more charts which show how the difficulty has gone up.

I use second hand S1 antminers, which are similar to 64 chips from the next higher model antminer-usb stick.  One S1 gets 160 to 200 Ghash/s depending on underclocking settings.  Whilst I do get hashpower envy every time I look up specs of an S5 or an S7, at least I'm within my power budget for home solar electricity experiments.
I can say that one S1 is about the minimum to see any output at all in a day from many BTC pools (or a month from some pools), and is better reconfigured with cgminer from hashnest and mining altcoins which appear in my home altcoin wallet quite frequently.  If for purposes of testing how it all works you need to see enough bitcoin to be allowed to transfer it to your home wallet, the S1 is probably the smallest sensible.  By the way, I also use it to help with warming up my computer room in the winter.

More specific advice from me I'll do for 0.1 BTC so pm me if you might want to buy configuration info.