I suggest the H17F driver from Mountain Electronics.
Not cheap, but in my opinion it’s the best clicky driver available. It pretty much has everything: Temp sensor, double-click shortcut, all modes fully programmable, multiple 7135 chips plus a FET. I consider it to be much superior to the BLF A6 driver.
Most common type of reflector for these triples is the Carclo 10507 (also available from Mountain Electronics).
You don’t need to purchase a separate lens to go on top of the optic. The Jaxman E2L host from Mountain Electronics comes with one.
For LEDs, the following will all work with the 10507 optic:
XPL HI - produces high lumens and the brightest hotspot.
XPG2 - similar beam pattern to XPL HI, but less bright.
XPG3 - Slightly brighter than XPG2 and dimmer than XPL HI. Gets hot fast.
Nichia 219C - gets very hot very fast. Very wide floody beam with much less throw than XPL HI. Can be purchased in high CRI
XPL2 - similar beam pattern to Nichia 219C, but brighter.
Personally, I recommend XPL HI in 5000K neutral white. The XPL HI 3A tint is a good choice.
The H1-A can reliably handle 2.5A for a triple, ≈25W, maybe a tad more but it may start having trouble with its 10A input limit and non-heatsinked driver ground plane (because of reverse polarity protection). To me this is no problem, that's already a nice lot of power for an E2L, and you attain fully regulated modes in a truly useable light without having to worry about blowing up emitters, PWM and other *cough cough* driver nuisances.
Honestly I’d only go with a boost driver only if he were going to use a higher voltage single LED at the moment. For now I’ll keep recommending the MTN17DD running Bistro and using the temp sensor. Once all the great folks here get a boost driver running something like Bistro/Biscotti then I will make the change.
I’d also recommend getting a few if not all of the Carclo 3-UP optics just so you can swap them to preference or based on use. I have an E2L with stock XP-G2s that I put the MTN17DD in and I prefer the wide frosted optic for anything indoors or up close. The narrow optic is actually rather concentrated.
I built my JAXMAN E2L with the MTN-17DD FET + 7135 driver with Bistro, Nichia 80+ LEDs, and narrow spot optics. I really like Bistro since it has up to 8 brightness levels (plus a great moonlight mode) and medium press to lower the levels. I don’t think the H17F driver has the medium press function which I use all the time.
For the battery, the Samsung 30Q will give you maximum output, but the Panasonic NCR18650B 3400mAh will give you a longer turbo time before it gets too hot. I would also go with a flat top.
You may also want to get the deep carry pocket clip.