1:10 active staff to active member ratio has been the golden number for me in the past.
Active being the key term, and for non-progression system sites it may be 1:15 or 1:20. For sites with no progression system and also not running site wide events frequently it may jump to 1:25 or 1:30. The amount of work that goes into making sure applications are up to snuff in terms of rules, running events and scenarios, distributing XP per thread, and general support though is something that I'd ideally want 1:10 active staff to active members.
People with more tend to count inactive staff as staff, which to me is pointless. Why would you have 15 staff members when 13 of them did nothing staff related in the past 6 months? I see it on a bunch of sites and it just blows my mind. Why would you give someone authority/power and then zero responsibilities? The power is unnecessary, then, and staff is used more like a social status symbol than an actual role with responsibilities if that makes sense. The logic seems to be that if you put all your 'core members' in staff roles it secures their place in the community even if they do nothing with those roles ever.
Staffers with a lot of time and know the system can do better, and staff with the opposite of that can do worse. I know someone who essentially solo staffed a site with that jumped from roughly 30 to roughly 70 active members during their six month stint as a solo staffer in a very stat/progression system site with constant events and that was nuts. They both had a lot of time and had a lot of skill in dealing with stuff and the discipline to never procrastinate even with their vast reserves of time. That is not the norm and most people, including myself, wouldn't even try to do something like that because it's silly and means that if the one staffer burns out from the massive amount of work then the site simply dies.
On my site I have one active staff member to fifteen active members -- alongside maybe five other members who I don't consider 'active' in the sense to where I rarely have to do staff related work to their characters because their posting speed is less than once a week so thread completion is infrequent. I could lie and say that I am a superstar staffer who does 1:20, but that's a misrepresentation because I get help from members volunteering to take on basic roles like calculating XP for threads or helping me do prep work for events so I don't have to solo run everything anymore. With the most tedious and thus most draining and the most time consuming and thus easiest to procrastinate work being split among people with zero staffing responsibilities but a desire to assist in basic tasks, it helps a decent chunk even if the metric is still 1:15 active staff to active members.
That being said, it's impossible to provide feedback on what might be right for you if there's no indication of how much work needs to be distributed per member. Grading applications on a full freeform site may take 30 seconds, whereas doing it on a stat-heavy site and if you're doing line by line reviews might take 30 minutes if there are a lot of errors and multiple revisions on the part of the player. If the former is all you expect out of accepting apps, then one person can deal with 100 apps quickly and easily by copy/pasting acceptance messages and then moving member groups. In the latter, 10 apps would represent an enormous amount of effort and would hopefully be split among multiple people.
| 
