Often, poor tasting assemblies have either one of two issues:
Below is a chart that will explain the optimal voltages for their correlating resistances.
Below is a chart of the most commonly used gauges and their respective resistance per inch.
It really depends on the coil head that you are trying to rebuild. The object is to fill the wick gap so that it is not so tight as to be able to see dark space inside of the head, yet not so loose as to let the wick move about freely in the coil head. Sometimes this can be tricky. A neat trick that works for most is to use 1mm wick as a measuring tool. 1mm wick wick is most commonly used for flavor wicking in bottom coil designs and will likely be handy to you later. You can use a few strands of the 1mm wick, coil it and then add a couple strands for flavor. Once you figure out how many strands it takes to get a setup that doesn't dry hit or leak, you've found your happy spot and know what diameter you should use in the future. For instance, if you coil 2x 1mm strands of wick and add 2x 1mm strands for flavor wick in you head and it works well, then you should be looking to use a single strand of 2mm wick as your coiled wick, and then the 2x 1mm flavor wicks on top.