If the ohms readings on the coil are all over the place, problem is likely with the coil. Try tightening the rda's positive and negative connections. Make sure coils are not touching the base or the posts. That could stabilize the readings.
Rebuilding: There is a free Android app called "Vaper's Toolbox," which computes how long to cut a specific gauge kanthal to achieve a specific resistance. It's not omniscient, doesn't do away with the need for measurements, but it's handy.
The resistance is up to you. I'd start with a single microcoil, and aim for anywhere from .9-1.5, but that's up to you.
There are hundreds of youtube videos on coil building and wick making. There are forums here on rebuilding as well.
28 gauge is easy to work with, and fine for most coils. Gauges lower than that are used by serious sub-ohmers.
Thanks for the tip about the ap, I picked up 100 feet of 28 gauge kanthal for only $11.50, so much cheaper than most of the shops in my area charging $3-4 for 2-3ft and sometimes the 2ft is is the $4 one. I checked you tube and see so many different versions of micro coils, I seen some people just pull cotton under the coils and wrap it around and some people who pull the cotton through the micro coil, I don't know if 1 way is better or not or right or wrong. I think I'm going to stay aroung 0.6-0.75 ohms for now but, not do anything crazy, I tried 0.2 ohms on someone's build and it's just too hot...yeah, yeah I know it's dangerous but just wanted to try a 1 drag, and I'm not going back to that.
Since you're just starting with this setup, you could be unfamiliar with the way the battery drains, and the way the whole thing feels. imo measure the battery hourly, and switch at around 3.5-3.6. People normally feel a drop in their vape quality, but if you're starting out with what sounds like zero vape quality, then you might not