How to estimate current consumption by ICs
The operational current means complete current consumption of IC. Even if not current consumption on SPI, I2C, etc. is very small, so you can not worry about it. Anyway, 1 IC won't cause power problems on Arduino, so you can connect it and measure current. Also, Arduino's power supply may be not enough for POWERING VCCs, of many ICs. Then you would have to use a separate power source, but it MUST have same ground with Arduino. So, you can't power, for example, Arduino from USB and your ICs' VCCs from a battery.