be careful with the mollies. as a newb i picked 3 because that fit my tank and they are community fish blah blah blah....well i picked a perfect breeding trio! I had 3 sets of babies before i knew what to do! thankfully, i found them a good home (through the forum). hopefully they are breeding excessively!!!
as for the salt, i guess i have impeccable water because i never had fin rot, fungus or the shimmies. i gave away all but one female fry. she lives with a betta, a rainbow shark, a pleco (Bristlenose, they stay small <3 in.) a japanese algea eating shrimp and an apple snail.
if you don't get mollies or if you choose to not salt your tank, look into african dwarf frogs. these guys are kinda cute. i always see them at my LFS but i haven't googled them so I don't know if they are hard to keep or what they get along with. mystery snails are good. cannulas are pretty, too. i would personally avoid rams of any kind....damned breeders only good for puffer food... loaches are good fish to get for a large tank. clown loaches are good but they like snails. yoyo loaches are pretty, but i have have not been able to find any so i don't know where they are sold.
i was impressed to see the varying kinds of aquatic life that could be put together. i have fish, a shrimp, snails, plants, daphnia (these are invertebrates that i would classify as freshwater plankton--don't know where these came from--but they are there for sure!) my tank is only 5 gal.
floating plants are nice. these and all plants need an aquatic plant fertilizer added to promote root growth. plants are good for the substrate too because they will use the nitrogen produced by the detritus that rots there. if you choose to buy plants, look for good roots. my LFS sold me a couple bunches of plants before i realized they had no stinkin' roots!
silly me. i should have though to check! they look ugly at first, but once you get it in your tank and cover the roots a live plant is a great addition.
my final tip of this long ass post: if you get plants and snails, buy algea chips/wafers to feed the snails or your plants are dinner item #1!!!!!!