Are you serious about trading using capital of only $3? it will just be a waste of time, unless you are learning to trade or testing your strategy. However, $3 is still too little, especially if you trade on the spot market. If you trade in the futures market, it might be better because there is leverage that will help your capital.

I don't use poloniex, but as far as I know exchanges usually have minimum limits for crypto purchases and can $3 be used to buy crypto? I think it would be better to increase your capital, maybe around $20 or $30, that's probably much more logical