All males will give you the most color but it is also challenging. When I set my 180 I had 4 extra tanks cycled and ready to go in case I had to remove fish. You will need at least an extra tank or easy access to a LFS that will take any fish back that don't work.
The males if you go that route should include NO FISH of similar color, they are co-specific (same color) aggressive, it is their nature.
If you don't go all male then in a 55g yes 1 male to 2-3 females of about 3 species giving you 12 fish in total.
It really does totally depend on what size tank you get...if you can get a 75g it would be ideal for a male-female group of 4 species or a good size for an all male peacock.
These fish will not do well in anything smaller than 55g and with the ratio I mentioned. In a larger tank it is best to aim for 1 male to 4 females.
Another thing to consider is where you will get the fish from...locally or order online?
The biggest concern at the moment ,is you need to know the tank size before I can really give a definitive answer as to what will work and what will not.