Ya if you can't go 75 I would probably go 40 breeder because of the 18" width, but a 55 is 4' long. I'm 13 too!!!! And have 150 gallon tank on the second floor...... My moms really happy with the weight lol. As for inverts, do you want corals? Of you want to be able to keep high light demanding corals like SPS
you're going to need really strong light. Which can cost $$$$$$. Anemones need just the same light. Also, I would recommend a CUC of hermits, snails, brittle/serpent stars, and maybe even some conchs (they're really really cool). Also some pep shrimp and cleaner shrimp would be awesome.