hi i used to have a fish only marine tank that was fairly successful,i set up just the same as a fresh water tank but added a protein skimmer and 2 light tubes ( 1 blue and 1 white ),the maintenance was easy too,i would go this route again if i was keeping larger fish (triggers,morays,lionfish etc),but for keeping clowns,dwarf angels,smaller tangs,gobies etc then go for a live rock based set up,really all you need is an aquarium,powerful skimmer,heater and good quality live rock,this is a bit simplistic but gives you an idea,the best advice i can give at this stage is to get hold of a good book i think a good one is 'the new marine aquarium' by mike palleta this will tell you in more detail what you need to know cheers
Paul