Hey
Saltwater is very expensive be prepared for high costs. I reccomend at least 29 gallons but preferably more depending on what fish you are interested in. Clownfish and Damsels are hardy and good for beginners.
Water changes on larger tanks can be done twice a week but it really depends on your set up.
live rock is great for biological filtration so i reccomend using at least 1 lb. per gallon in you tank. With live rock you dont need a Wet/dry or
trickle filter. You need a protein
skimmer though.
Lights will run you quite a bit depending on what you want. If it is a reef setup the lights on just a 29 could get up in the hundreds if u want harder corals like
SPS.
If it is Fish only w/ liverock then u should be cool with standard flourescent lighting.
You will also need sand, just enough to make a good somewhat thick base.
And Salt and a SW testing kit.
Also you will need to either buy purified water or get an R/O + D/I filter.
Thats all i can think of now. Plz post more specifically what set up you will be using.