Akueck has "hit the nail on the head". 2 and 1/2 to 3 and 1/2 lb per gallon are good guide numbers, but I'd also add that it's probably better to go for the lower end initially and then check the mix with a hydrometer. Over at
WaH, they recommend sticking to a lower gravity to start with, usually about the 1.080 range, because they (well Bob who runs the site) likes to recommend a method where you will have a success on the first attempt as it almost guarantee's that you'll get bitten by the bug.
Hence if you started a batch at 1.080 and fermented it dry (taking 1.000 as dry) then an 80 drop would give you just under 11% ABV, but most of the recommended wine yeasts would easily ferment down to 0.990 so that would be a 90 drop and just under 12.5% ABV.
Me ? I like to recommend/suggest somewhere in the region of 1.100, which taking the 1.000 as dry still give you about 13.5% ABV but is a low enough gravity to be able to manage easily on your first attempt.
Of course, it's fair to point out, that using gravity (or brix) measurements is to allow for consistency. Because if I make a gallon of JAO, it's usually a little less sweet as I automatically take "gallon" to mean an imperial gallon or 4.55 litres, whereas you'd probably take it to mean US gallon or 3.78 litres - which would give you a slightly higher honey to water ratio, and logically a little more residual (unfermented) sugar.
If you went for a traditional mead and fermented it dry, it can then be back sweetened later to bring it up to the desired level of sweetness that you're looking for. Me ? I like my meads sweet, to between 1.010 and 1.020 - whereas the commercially made meads I've tasted here are all "dessert wine" sweet at about 1.035 to 1.040 - they're far too sweet for my taste.
If you go for JAO, you will end up with a sweet mead, which probably will be fine as the acid from the orange often reduces the apparent or perceived sweetness - and sticking to the recipe and method "religiously" will almost guarantee you a good first attempt. Don't be put off by comments about orange pith and possible bitterness - I suspect that is part of the design, the acid and bitterness helping to reduce sweetness.
It's your choice of how you'd like to begin.. Good luck with your early efforts and of course, welcome to Gotmead.
regards
fatbloke