Must buy? Two wetbox, one for backup since it's a great device
I have 3 batteries (14500), it's quite enough, they only take 2 hours to recharge, the multi-charger can hold 2 batteries at the same time, I recommend the TrustFire charger, I had a charger but it's no good for 14500 batteries, these are very special batteries.
Get as many empty bottles as the number of liquid you are vaping.
It should be same thing for the needle if you don't want to swap needles with bottles, it's a little bit messy when swapping. But they are more pricey, get at least 2 nonetheless. I have 2 and will buy 2 more because I only have 4 type of liquid that I'm vaping.
Then happy vaping!