ya i know whta you mean...(i'm only 17 and i dont have money either)
in that case..you should just add whichever one you would like to have first...i think that royal grammas are somewhat skittish and dont come out much for a while...and i did hear that they dont like a ton of light...i would prolly do the clowns first, but mostly just cuz i like those more.
80 gallons is plenty of room for these 2 fish, as they're both pretty small. The clowns (are you getting percs/ocelaris, or are you getting something like maroons?) can be pretty territorial, but not aggressive...meaning they will protect their space...they can also hold their own w/bigger fish..they can dish out quite a bit for such a small fish (they're related to damselfish, so i'm guessing thats where they get that from lol) But they wont go "hunting" for fights so they'd be fine first.
the royal grama..i havent read a whole lot on them, but i dont remember ever seeing that they were territorial, and i know they're not aggressive, so i would think that if the clowns have already established a spot, the gramma wouldnt care...it would just go somewhere else.
also, for the clowns, i think that once they find a good spot, they kinda dont stray to far from it...other than feeding time of course lol.
hth