1st, i wouldn't get a 110 gallon until you can sucessfully keep the 30 gallon. as of right now, you can't and you're going to waste a lot of money and kill a lot of fish.
2nd. what equipment do you have? you should have a hydrometer (prefered) or swing arm salinity tester, test kits for ammonia, phosphates, ph, nitrates, nitrites, alkalinity, and calcium, digital thermometer, two to three 5 gallon buckets, fish net, plus other stuff like heaters, powerheads, lighting, filtration. you should also have SEA SALT (not table salt) and decholorinating products (really should have a reverse osmosis system)
You should also get a 10-20 gallon and set it up as a quarentine tank, or use your 30 gallon once you get the 110 up and running.
3rd what fish store are you dealing with, if it is ***** STOP listening to them.
how to set up your tank: dechlorinate your water or buy ro water, put your water in a large tub with a power head and a heater. slowly mix in your salt to a specific gravity of 1.026. fill your tank half way. put your rock and sand in, then fill the rest of the way. run your tank for at least 2-3 weeks watching your levels. once you are down to zero on ammonia, nitrates, and nitrites you can add your cleaning crew. wait a week and add ONE fish (or a pair of clowns). make sure you are doing 10% weekly or 20% bi-weekly water changes using the premixed water you have in your large tub of water. you should use fresh, dechlorinated water to top off your tank from evaporation.