That's a somewhat complicated question to answer.
Exactly how many honeys will be good for your tank depends on what else you plan to put in there - particularly as far as other top-dwellers or other gouramies are concerned. Do you know what you are going to stock yet and how many of each? Even an approximation would be better than nothing.
Lets also clear something up - you are not reffering to the dwarf gourami (colisa lalia) that has various color morphs with the name 'honey', 'red', 'red robin', 'flame', 'flame honey' etc right? The fish you are asking about is the true honey - colisa chuna/sota.
A few other points - honeys only get to 1.5" and, as only the males are territorial, you could, in theory, keep a pretty big number of individuals in a 50 gallon. To give you an idea of what I mean, a trio (1 male, 3 females) works in a 10 gallon.
That also brings me to the next point - it's generaly best to go for a ratio of 2 or more females to every male. It doesn't matter whether you wish to breed or not, this is about deviding aggression and keeping the females from becoming overly stressed. It also means the territorial males are preoccupied so they don't bother each other.
If you were to go by that ratio, a species tank containing 50 gallons could, in theory, hold about 15 individual honeys

... Though a lot depends on surface area and how accurately you sex them
Which brings me to the next point

... Sexing juvenile honeys is virtualy impossible visualy. That means you are likely to make mistakes and end up with the wrong ratios. What I suggest you do, if you want a reasonable number of the honeys, is to get 2 males and 4 females to begin with. If you find you have extra males, you can add some more females in future. If you find you have more females than you'd like, you can add a few more males. The only thing to keep in mind is that, whenever you add new gouramies to an established group, you should add at least 2 at a time. This ensures no single newcomer is bullied. Also, when you add new gouramies, they should be about the same size as the existing group. Again, this is for aggression issues. If you are not keen on ending up with 5-8 honeys, start with a trio - 1 male, 2 females - and see how things go. If you realy need to, you always have the option of returning a fish and replacing it with one of the right sex. A group of 3-8 is about right for a 50 gallon community assuming they get the top layers to themselves and no other top-dwelling or related gouramies are included.
As for how to attempt sexing them; the best you can do is look for the brighter ones and assume them to be male and take the paler ones for females. Younger fish will all look pretty much identical and the color won't realy be a reliable indicator. You'll also notice that all young fish have a horizontal stripe along their bodies which only remains apparent in females later in life. The fins can also be useful as males have more pointed and longer anal and dorsal fins but the difference isn't as obvious in honey gouramies as it is with other species. I find the body shape can also be useful but, again, only older females will show the wider (look down from above) belly and deeper body when compared to the slightly slimmer, lengthier-looking males.