$2,000 is better but even that's rough. Consider you have $7 commission. With each $1,000 purchase, you have to earn 0.70% just to earn back that $7. If you sell that $1,000 purchase, it'll cost another 0.70%, totaling 1.4% in fees.

Based on your strategy you're probably incrementally purchasing and the selling in bulk so the sell commission isn't as damaging but losing 0.70% of an investment right off the bat makes it hard to be profitable. Even half that amount, if you increase your lots to $2,000, is painful.