Just remember, you get what you pay for.
Also, never buy GTL or any other battery that exaggerates the capacity by stupid amounts, best to just avoid ebay for those battery types.
Find out what the best name brand battery capacity is at the time and go from there.
Expensive, but a good brand and trustworthy seller.

For batteries, read this guy, then buy Panasonic 3100mAh from a genuine supplier.

http://www.torchythebatteryboy.com/p/18650-batteries-chargers.html

for chargers, buy this.

http://www.nitecore.co.uk/Shop/Products/Batteries-AND-Chargers/12347-Nitecore-Intellicharger-i4-V.2.html

All the chargers on DX are shit. That’s the technical term, they are all underspecced, poorly designed, not fully heatsinked/ballasted and generally ready to kill you from the second you plug them in.

The panasonics and Nitecore might be far from the cheapest bits you can buy, but they do happen to be the best. I run a 1200lm light and one of Trouties original 2100lm lights.

Cheers 😀
Seriously, I bought my little torches several years ago, I can’t really remember now, it might even be four, and I got six batteries, the TrustFire ones, at the same time, and they’ve all been faultless, I’m still using them now, the torches are nearly always in little Fenix holsters on my belt, on various shorts, combats, jeans, etc, the perfect EDC torch.
I have got a few of those blue Ultrafire batteries, and I must admit, having read the stuff by Torchy, that they’ll be retired very soon in favour of the TrustFire 18650; mine have been in use even longer than the 14500’s without issue, so maybe, because mine are DX ones, are more trustworthy than eBay ones, I honestly don’t know, but I’m not so trusting now.