Let me give you an example of the difference in higher end vaping gear, and the lower end that you are currently using. Note that both can be satisfying in the long run, choose whichever route you find most satisfying.
Part 1: The Replaceable Battery Unit
Lots of options in this area, from the cheap, to the expensive. For this example, we'll use something in the middle of the pack, the Innokin iTaste SVD. The iTaste SVD is a sturdy and capable unit that costs about 35-40$ new if you SHOP AROUND to find the right price. That's a 40$ investment, and it WILL NOT work without batteries, which it does not come with.
iTaste SVD: 40$
Part 2: Batteries!
Here are the replaceable parts. For this, MOST people will end up using EFEST batteries, or SAMSUNG 25R, or LG HE2. Using the largest battery for the SVD, you would want an 18650 sized battery, flat top, unprotected. All three of the batteries I listed come in at or below 10$ each. They are rated somewhere between 2200mah and 3100mah each, but for budget purposes, I would start with the 2500mah batteries. Two is a good starting point, three is better. Lets call it three.
3 2500mah Unprotected (IMR) 18650 Batteries: 30$
Part 3: Charger for the batteries!
Battery safety is important, which makes investing in a good charger a good idea. An XTAR WP2 II is a good place to start, although people will tout other chargers being better (Nitecore chargers come to mind). Around 20$ is what you would look to spend on one of these, less if you shop around. Two bays = able to charge two batteries at one time. Big plus.
XTAR WP2 II: 20$
Total cost: 90$
With that setup, you would ALWAYS have at least one fresh battery to slap into the SVD when the battery in it is drained. These batteries will likely last far longer than your 900mah egos. The SVD will accept Ego or 510 threaded clearomizers, which you already have 4 of. The replacement batteries, when treated properly, can last up to 300 charge cycles, and even then, 10$ to replace one that isn't holding a charge anymore? Not a bad hit to the wallet.
All in all, these kinds of mods are a higher up front investment, but lower cost in the long run because the batteries just aren't that expensive.
Note that everyone's experiences vary. Learning about batteries and the settings available on a variable voltage/variable wattage advanced personal vaporizer, like the Provari or the SVD, takes time and some commitment.
