Usually the cheaper, older, USB sticks work best. I use an old Kingston 8GB USB stick, for my duo 2.
There are that many cheap, Enigma 2, receivers, that are cheap, that it's impossible to recommend one. It all depends on your future needs, e.g. is your TV 4K, as you might want a 4K receiver, do you want an internal hard drive, for recording, quite a few have HDD caddy's where you just slide a hard drive in, and out, so can be quickly replaced?
Do you need multiple tuners, so that you can record a channel and still view others?
You need to work out a budget, and what's most important, to you.