So far, in the last 5 days, I have used about 75 % of a 30ml bottle of juice. So I think that's alot. About 20 $ in the last 5 days, plus 5$ for a coil, so 25$. I would have spent about 30$ for smoking in the same time. So not that much difference I guess. I'm ok with spending alot since it is better for my health, but ideally I would like to also save money by vaping. My friend told me I will eventually vape less, and probably I am just doing it alot to start.
That's around 4-5 ml a day, which isn't excessive at all. You may end up vaping less, maybe at a higher nic level, or you could end up consuming more. Also, if you are sub-ohming at a high wattage, it uses up a lot more juice than vaping at a lower wattage / higher ohm, so it's sort of difficult to say. (I use 1.6 coils and vape at between 10-15 watts, for example.)
Also, some people (like me!) need the physical action of smoking/vaping more than the nicotine, eventually. I quit smoking SO MANY TIMES, getting totally clean from the physically addictive elements, but was always drawn back -- less for the chemicals than for the muscle memory of picking up and puffing. So I vape a
lot but at low nic, sometimes even zero, because I want the comfort of the action itself. Obviously this means I go through more juice than someone who just needs a nic bracer now and then.
I have disagreements with your starter rig. I wouldn't start someone new (or newish) with a sub-ohm set up. I would put an eLeaf iStick or Pico in your hand with a Nautilus mini tank on it. Really easy to transition from smoking to vaping with this. Super reliable, easy to deal with, and not expensive. If you were my friend and I wanted to help you quit smoking, I'd give you this from my own stash, and watch you happily stop smoking (probably) without a lot of complications / overpowered stuff getting in the way.
At any rate that's probably a matter of opinion. In terms of savings, eventually, you might decide to start trying out rebuildable tanks and make your own coils. At that point, coil cost goes down to negligible. But give yourself a chance to get comfortable in vaping vs smoking mode before getting into something that might prove frustrating at first. Same with e liquids. You can make your own and save tons, but negotiating the transition between smoking and vaping and trying to figure out the basics of new skills can prove frustrating enough to go back to smoking. So Step One is always just get a set-up that works well for you. It needs to be easy and comfortable to pick up the vape instead of the cig.
Step Two is read up, hang on the forums, watch vids, pay attention to what people are talking about. It will all be gobbeldygook and even sort of scary in the beginning, like omg, I will never be able to do (or even understand!) X. And TRUE some things you will likely never, ever do! Some things will likely remain Advanced Gobbeldygook! And that's totally normal! People tend to eventually explore the stuff they are most interested in, and you will find that out in a natural way as you go along. Job 1 is just Not Smoking. Any way you do it that is Not Smoking, is the best way! But step two will help you find the options for personal vaping, the vendors, the deals, the trends, the tried-and-trues.
Step Three (optional!) is begin to try a thing or two that aren't vaping 101 that particularly interest you. You ask questions, you start experimenting. Because you are already totally comfortable NOT SMOKING, you are good with what you have now, it's absolutely doing the job, but you are curious and/or getting a little restless with your own status quo, or want to get more frugal. That's great! That's fun! That's a hobby, for many of us. But it's not necessary to do in order to quit smoking and start vaping. Congratulations on your progress so far! Don't worry about costs right now; soon you will be able to evaluate better, but at the moment, only spending as much as you did on the killing stuff is a total win!
Use your own senses, if it's harsh to you and a new coil fixes it, that's how long a coil lasts you 
