OK pocket carry and 800 lumens that narrows it down. How about the Uniquefire UF-2100 3 or 5 mode? I have the Yezl version of this light and it belts out an honest 800 lumens and fits in your pocket. Here is the test.
Here is a really good price on the 3 mode version.
The 5 mode version.
You are also going to need at least two 18650 batteries and a charger.
I recommend protected Trustfire Flame 18650s to start out and a Trustfrire TR-001 charger.
This is the TR-001 charger I have bought a couple to sell and kept one for myself, it is my go to charger very reliable safe and cheap.
For batteries I own about 20 of these Trustfire protected 18650s again very powerful reliable and safe at a reasonable price.
I don't typically recommend DIno Direct for a vendor but they have some really good prices right now and they have been stepping up there game. Check around they have posted some decent coupon codes on BLF find one and use it and you can get a great deal on an awesome starter light setup.