I have this machine. Bought it via amazon (I don’t recall the particular seller, but it was a “fulfilled by amazon”). I have been satisfied. Decent dimensional results, and after two rounds of bed leveling, I have not needed to adjust (second round was in December’18)
For my use, I primarily use PLA, because it suits my needs, but also use HIPS when I need better mechanical properties. PLA has got much better over the last 10 years or so (consistency of properties). Note that is really isn’t recycleable in practice, any more than other plastics in these applications. The primary advantages for me are lower temperature and solvent resistance, relative to ABS and HIPS (and others). Lower temp means faster print times and less distortion. I got the magnetic bed mat (only use with PLA. Despite the documentation, I tried it with HIPS and found out why they say not to…) and it is the cats meow with PLA.
I would suggest starting with PLA, as it is MUCH easier to get satisfactory results (for the reasons above) than most other filaments. I have not tried Nylon with this machine, but may need to soon for some gears.
How much filament to buy really depends on how much you will use the machine. I am not a high volume user, but still run through 1Kg in about 2 months. I can’t speak to brand, since the environment I work in is maintained at 30 to 40%RH (and my power bills show it), so moisture pickup isn’t a major issue for me at home, and I have found that all of the PLA I have used over the last several years has been similar. Maybe I have been lucky. I store HIPS in a dry box (desiccant controlled) and will store Nylon with it, as even 30%RH will be a problem, given the long storage times. This is a pelican case with a large desiccant sack (color indicator type). Inexpensive and pretty much air/moisture tight.
At work (job 1), we might run through 1Kg in a few days (machine is a LulzBot mini. Too rich for my wallet for home use, and, honestly, the results are not really much better then the Ender) on each machine. Students can burn through a LOT of consumable. Storage after opening isn’t an issue, even with poor RH control.