Batteries degrade with time. Depending upon usage, you should plan on replacing the batteries for any of the standard cigarette-looking systems every 2-3 months. You can prolong this by getting more batteries and rotating. So if your current system was working fine for you before but isn't now, you might consider just buying new batteries for it which would be a very inexpensive solution to the problem.
For cigarette-like systems, which is what I prefer, I like the following configurations:
510 Mega (280 maH) battery with 510-T atomizer and 510-T cartridges. (You need a syringe and e-liquid for this.) If you get four batteries, a charger and a PCC you'll have a complete go-anywhere system.
808d-1. I like V4L for superficial reasons -- many color options for batteries! Don't get the super-short batteries. Get a couple boxes of CE2 Rev4 cartos and a syringe and e-liquid. Again, get four batteries, a charger and a PCC for a go-anywhere system.
(The 510 and 808 refer to different thread types on the batteries. The 510 is a female-threaded battery and the 808 is a male threaded battery.)
I have never needed more than two batteries in a day with these systems. The reason for getting four is to rotate the batteries thereby extending their useful lifespan.
I also prefer manual batteries, especially with 808d-1 systems because they seem to give better performance. On the 510-T system the auto mega battery actually works okay but the manuals still have performance advantages. Still, if an auto battery is your preference IMHO the 510 autos are better than the 808 autos.
Both of my recommendations are "tank" type systems. They are easy to refill without the headaches of burnt polyfill, etc.
But, again, before looking at these, I would strongly consider just getting replacement batteries for your current unit is your current unit was working well enough in the past.
