Most drivers just use the basic card readers, I think.
You should get one for about £30 or so with p&p, or maybe even cheaper when they're doing deals.
Basically they seem to price them cheaply to suck you in (the small print normally says its for 'new eligible business user' or similar) and if you damage it or need more than one reader then you'll need to pay the full price, which is probably more like £70 or so.
Never really used the phone tap facility myself, but the card reader will read the usual cards, phones and watches etc
Generally that will work, but sometimes it requires the card to be inserted and maybe a PIN, which is maybe just a random request from the bank, or because the particularly card doesn't suppport contactless payments.
Sometimes it might not work first time, but will work if you just go through the process again.
Some people will ask for a receipt, and all the readers/apps have a facility for email receipts (I'd guess). I normally hand them the phone, where you have to key in the recipient's email address in the app, and it's generally easier from then to do it quickly and accurately themselves rather than you doing it, and most people will be happy enough with that.
(The odd person still asks for an old-fashioned paper receipt, though...)
And, of course, it helps to be using it with a phone account with good signal and coverage, especially up in your neck of the woods. You'll get a feel for where coverage/signal might be dodgy, and to that extent it's also good if you know your mobile provider's coverage map reasonably well for possible blackspots. And if you know the signal might be a problem then it's often useful to ask for payment in advance, although that's potentially awkward (like tipping) and needs to be done diplomatically
