Welcome to Reef Frontiers!!!
I agree with Krish. The number of fish you want, will partly depend on the species of fish, and your goals for the tank. As an example, in my 120 US gallon tank, I have 6 fish (2 clowns, 1 6line wrasse, 2 anthias, 1 rabbitfish, 1 tang). I would probably only add one more fish in the mix (depending on mature size, maybe 2). I also don't want a high bioload. 2 of my fish will be big, and I want to give everyone a good territory to play in.
What are you thinking about for the tank? Maybe if we start there with fish you like, we can see if they will be compatible with what you want to do. Also, tell us about your filtration (skimmer, live rock, substrate, etc).