@mmhhhkkkk
Hmmm, good question! I think with most jobs, people should be there 5 to 10 minutes early. In order to hang up their coat and bag, maybe grab a coffee, and set themselves up.
However, there's a very thin line between coming in a bit early, and people taking advantage ... (trying to throw work stuff at you when you haven't started yet.)
Some years ago, I had a job that started 9am, and finished at 4.30pm (half hour lunch,) and my bus got me there at 8.35 to 8.40am. If I'd got the next one, I'd be there at 9.05am, so too late. Several people started at 8.30am and had an hour lunch, I chose to start at 9am and have half hour.
At least once a week, someone would badger me as soon as I walked through the door, with some work related shit. I'd say 'I don't start for 20 minutes!' But it didn't stop them!
The shit hit the fan this one time, when my manager made an appointment for me with a client for 9am. The second I started work. (I usually preferred 9.10am for the first one...) He instructed everyone else, to not start HIS appointments until 9.30am, but mine were 9am. 
Anyway, this one day, I got in work 25 minutes before I started, and my manager said 'your nine 0 clock is here, go call them in from the waiting room.' I said 'but it's 8.35am, they are nearly half hour early.' He said 'and??? They are here, and you need to see them, and not keep them waiting 25 minutes!' I dug my heels in, and said 'their appointment is 9am! If I hadn't walked in til 8.57am, they'd have had to wait 25 minutes then!' He said 'just call them in.' I said 'NO.' He was fucking fuming because I refused. I literally did NOTHING wrong, so he had nothing on me, and no reason to 'scold' me.
After I HAD seen them (I did at 8.45am in the end!) he called me from his office, and said 'we need to talk about your attitude earlier. Come into my office. NOW.' I said 'no, and carried on working.' He said (loudly) 'ARE YOU ACTUALLY LOOKING FOR THE SACK?' I said 'on what grounds??? Go on, report me to the area director, and we'll all meet together, while you tell me exactly what I did wrong, but no I am not coming into your office. I've done nothing wrong.'
tl;dr. Basically, it's not uncommon for other people to take the piss if you're too early, and expect you to start work early. So I would never be more than 5-6 minutes early.
By the way, my manager stormed out in a rage, but nothing else was ever said. It was WEEKS before he spoke to me normally though. I didn't care. I didn't like the twat anyway. I'm not always very assertive, but can be, and no WAY was I accepting bollocking for nothing.
Also, this wanker of a manager used to glare at anyone leaving ON TIME too, and not wanting to take a phone call or see someone at reception 2 minutes before their finish time. He never did - but expected others to. He often stayed after half five though (when the office shut,) sometimes til 6pm, as it kept him away from his wife and kids, but he regularly went off for lunch at midday and didn't return until 2.30 to 3pm. Fucking arsehole he was.