>As long as the money i spend on the card is less than the money i place on it i only have unrealised capital gains.
Either you aren't in the US, or you don't understand how capital gains work. What you describe is exactly a taxable event (could be a loss, could be a gain).
Selling X shares of a capital asset for $Y is always taxable, no matter if you also buy X more shares, or $Y more in the same period of time. See also: wash sale [0].