Its going to depend on a few things. Airflow, chamber size, how low you go.
You need to have a good reliable way of testing your builds resistance, suitable cells and a way of checking your cells are safe for your build. Cover all tjose and your pretty much sorted. Do research on your chosen atty, see what others are using in those attys. I sub ohm everything, but I also have wide open airflow and lung hit everything, for me, most of my builds are "warm" which suits the juices I vape, for me, its a very subjective thing and dony feel you have to sub ohm just because you have a mech, you dont.
So. Your going to want good cells and a good charger. I personally rate the efest and xtar chargers and wouldn't even use an intellicharger to throw at next doors dog.
Cell wise, I only go for manufacturers cells - sony samsung panasonic lg are a good place to start, my next rule is can I easily find the manufacturers data sheet. That will tell me the important bit - continuous current limit. I dont buy into the new theory of pulse limit, it just strikes me as folley. Your going to want a limit of between 20 and 30 amps although I do use ten amp limit cells, I ensure they dont see a build lower than .6ohm, still a satisfying vape and huge runtime. We are talking 18650 cells, I would personally forget anything smaller, they just dont work.
Next is airflow. If your dripping you want at least 1.5mm per coil. My current drippers are clones (trident and omega and monster cloud) and my double cross (insane airflow) the clones start with the monster cloud at 1.5mm per coil (quad coil bastard to coil) then the trident at 2mm per coil and then the omega at 3mm per coil. Tanks I use a drilled out kayfun at .7ohm as its got a stupid tight draw, taifun at .6ohm with the airflow tube removed and aqua at .6ohm and stock air holes. I also use and aga t3 at .7ohm with the airhole drilled out to 2mm. Prometheus is a really good sub ohm genesis tank, easily good down to .2ohm.
Next your build. You want to be able to check it. Most variable wattage devices will do this, next is the cheap resistance checkers and the ideal is a good multimetee. Remember with the meter to check lead resistance first then subtract the lead resistance from the measured resistance to give coil resistance.
Once you have your coil resistance, feed it into an ohms law calculator with 4.2v as your voltage and this will tell you your worst case current draw and power if you use vapers toolbox on your phone.
Do all that and then you'll know if your build can be fired. Dont at any point think "fuck it, it'll be alright" make sure you know it'll be alright first and you'll be safe.
Hope all this helps. @
Raguri is good to help on this, he's way dafter than I am. Let us know if you need any help