Ah, well, if you're just looking to have some fun and not really into generating btc, get a gekko sidehack stick. The sales reopened lately so it would be a good usb stick to learn some basics mining concept (maybe).
You could try to get some U3 but its not really a great miner for a couple of reasons. Maybe 20$ each could be worth it.
They go for around double that currently it's going to be around 40ish on most u3's. So you are paying for a lotto machine and chances of profit or even ROI is slim.
You need to look at a bigger machine if you want ROI. Price per TH is just a lot cheaper. Yes it's more expensive but if you want chance at ROI you have to do it. Also with U3 they are a pain on zombie you need some automation on reset unless you enjoy babysitting gear.