That kinda depends on your tank size, time available and patience. Some fish will do the breeding whether you do anything or not, others are close to impossible.
P.
i think you need to choose what fish you want to try and breed, which fish will do best in your water pH etc... then look into how to go about it. some fish breed in almost any conditions like platys, guppys, endlers and so on and some need really spot on conditions. then there is always the chance that they will just not breed for you, it all depends on the fish and conditions etc. although not everything needs to be done by the book as my corys proved, they are in a pH of 8 and according to the data presented by people, internet, books it needs to be at about 7. so if the fish are happy then they may breed for you. there is also quite a lot of work involved before and after eggs/fry as they need daily water changes and feeding regular and also their own fry tank, growing out tanks and equipment. if you want to breed to sell then it may be worth trying something a little bit different than the norm as lfs really dont want to pay much for fish from private breeders as they can get them really cheap from importers and some just wont buy from the public....
good luck with your choice and i hope the chosen fish do well for you
Your best bet is to reverse engineer it. If you don't have an outlet for the fish you have bred, what will you do with them? Find which species are desirable in your area.
Next, since you are just starting, determine which are the ones that are easier to breed, will do well in your water, and that you have the time, funds, & tank space required for breeding.