Oh man, you caught me at a bad time - I have a lot to write but my desk is currently covered in stuff right now - I just got 2 new RDAs in that I'm cleaning building decks on. I'll link a few things right off the bat, because batteries are in quite a short supply right now. I would order some ASAP.
Molicel P26As are my go to - I have 20 or so floating around right now, and 10 of the P28As (little more capacity, but hardly noticeable for the price difference). If you're planning on vaping around the 50-75W area, these will work perfectly.
I'd buy a bunch from Liion or 18650batterystore right now - they're close to the same price, so I'd throw them in the cart and see what shipping comes out to.
Liion -
Molicel/NPE INR-18650-P26A 35A 2600mAh Flat Top 18650 Battery - Authorized Distributor
18650batterystore -
Molicel P26A 18650 2600mAh 35A Battery - 18650 Battery Store
Also a heads up. Earlier this evening, I linked the Molicel 21700 P42As in a different thread. The last time I posted it, they were gone within the day, so if you are planning ever using a 21700 mod, I would suggest also grabbing a few of these as well. It could be weeks to months before the next supplier gets some back in stock.
Liion -
Molicel/NPE INR-21700-P42A 45A 4200mAh Flat Top 21700 Battery - Authorized Distributor
If you do plan on getting the 21700, then might as well just get both from Liion. I will link the rest of the reputable stores that Mooch suggests later if you cannot find them. For now, just grab these up quick while they last.
Good choice on the starter kit - I had that exact kit sitting in my cart the other night after I linked it to you, but I simply have too much stuff sitting here that I don't know what to do with quite yet, so I'm trying not to add to the problem. That tank you're getting, you're going to be very happy with. It competes very heavily with (and actually beats many of my RDAs, disregarding the fun of building the deck) in flavor and clouds. I would grab a spare 5 pack of 904L X or M series coils. I don't recall the exact ohm range between them, but anything from 0.15 to 0.4 should be fine. Oh, I forgot the charger I use. Let me look where I bought it - it's one of the only ones I could find that has a 4 bay 1 and 2 amp configuration. There's also a 2 bay version that does the same. I'll tack that on the bottom here when I find it.
XTAR D4 Battery Charger - Wholesale Discount
It's a few bucks more here than at IMR or 18650batterystore, but if you can get the Molicel P26A, P42A, and the charger all at once, I'd suggest just getting it here. You're likely to pay that extra cost in base shipping elsewhere anyway. up to you how you want to shop it.
So, quick run down on this battery charger:
It has 4 bays (battery slots). Bay 1 and 4 charge at 2amps when only those 2 bays are used together. Bay 2 and 3 charge at 0.5amps when only those two bays are used. When all 4 bays are used at once, it charges at 1amp. For singles, it defaults to whatever the paired charge is depending on what slot you're using. Bay 1, 2A. Bay 2, 0.5A. Bay 3, 0.5A. Bay 4, 2A. Charger is compatible with pretty much every common flat top battery type there is:
14500, 14650, 16340, 17335, 17500, 17650, 18350, 18500, 18650, 18700, 20700, 21700, 22650, 26650.
There's also a 2 bay charger of the same type that also charges 0.5, 1, and 2A as well based on 1 or both bays in use at Liion called the D2, but they're out of stock atm.