it's alright. practice makes perfect!
imo, i think text looks best when it's simple and in a spot that's not too busy. before you put text on a graphic, look at what spots look empty or missing something and plan accordingly.
i also prefer a maximum of two or three fonts -- anything more than that and it's just too busy.
and .. as for what "looks right" .. just think about it. try different things. i can spend the longest time on text before i get a result i like.
song lyrics or quotes are always a good thing, provided they're fitting to the graphic.
idk if that helped, but keep trying

you'll get it eventually.