Just a note, any good mod you're going to want (not necessarily need but surely you should) buy an external battery charger. Without it you can imbalance your batteries which is bad, over time that will be an issue.
So chalk up $20 there, then the batteries, another $15-20, you'll want something like LG HG2's, Samsung 30q's (equivalent to HG2s even if the company specs say lower, they're just doing that for safety), or Samsung 25r's. $10-15 will get you the batteries but having a backup pair to rotate with is mighty nice.
Then you jump to the mod. At .3Ω there are a lot of options. For price point an iStick 100w should treat you very well. The Cuboid is another great cheaper option. For best bang for your buck the RX200 is great, though you'll be spending more on the mod as well as needing 3 batteries per set rather than 2.
Main point of my post though is to point out that initial investment. Now there are fixed battery/lipo cell mods, the replaceable lipo cell options are generally more expensive DNA chips so that should be ruled out, but then there's the fixed battery options. You may be able to find one and save some on the initial investment but over time those batteries will wear out and then you have to just chuck the mod and buy a new one, with a 18650 mod you don't. You chuck the $5(each) batteries and grab new ones and keep on chugging away. So in the long run it's worth it 6mo-1year it'll pay for itself.
All that said, you may be able to find a good passthrough mod that you can charge on, with a single battery that avoids some of the concern of using a mod to charge (the other is safety, it won't be as good at cutting off the power once fully charged). And, then you're down to just buying 2 batteries to rotate, or even just one that you rely on completely.
Either way just some info to consider. An iStick 100w is like $25-30, a cuboid (much better) if you can find it on sale you may be able to get it at $30-35, though what I'm seeing is closer to $40 right now. Kanger is also not a bad option, but again you'll still need to buy batteries and want the external charger.
