Artix - 7 Voltage Specification I/O standard
You must supply VccInt for all pins named "VccInt". This is internal operating voltage and is not available on the outputs.

The same applies to all Vccout I/O banks as well. All Vccout pins must be provided with voltages. Each I/O pin is designated to one of the device's banks, and each bank can have a different voltage, based on your needs (but, of course, must be a standard, i.e. 1V, 1.5V, 2.5V, 3.3V... and acceptable by your device). For example, if you provide Vcc bank_1 with 1.5V, the logical levels on all pins of this bank will be 0V and 1.5V. In general, you choose the bank voltage depending on the standard of your peripheral devices - to avoid voltage shifting/translating. Thus, if your DRAM I/O is 3.3V, it will be convenient for you to power the bank, to which this memory is connected, with 3.3V.

Vccaux - is used for JTAG. It must be the same as for JTAG cable, and, of course, must be in the acceptable range of the device. As for the other voltages - you do not need them at this point - the device will be able to run.

Vin - I/O input voltage (not power supply). It's a logical input high/low (from external devices). The voltage on the pin should be the same as the Vcco voltage of the bank to which it belongs.

Vref - can be provided to universal IO pins when you use differential input buffer. I never used it, so if you have to use it, you will know about it.

Vrefp - I would says that it is the same as Vref, except it emphasizes on the fact that is it "positive".  

Check DS181 table 2 and UG471 p.17 for more information. You will need to at least skim through several datasheets for kintex7 to get started. And pay attention to the specific package that you are going to use.

Here's some info about IO Standards. Check more internet sources. Kintex allows multiple IO standards so it can be easily interfaced with other peripherals. As for Gigabit Ethernet - this is a separate topic, which I know nothing about. I would suggest you starting from here.

NOTE: This is general information for the Xilinx  devices. Please, refer to specific voltages in the datasheet, as they vary with device package. 

Also, keep in mind that you need a configuration memory for you FPGA, since it does not have one within the package.