Discus are hard to keep and not recommended for a beginner, especially as you say the only fish you have bred are platies and I suspect you didn't specifically breed them, they just did it all by themselves requiring nothing specific by you. This is not to put you down, just saying you have jumped from an easily bred fish to one that is a lot more difficult with specific requirements. You seem to be going all over the place in your ideas for fish to breed. I suggest you sit down, decide exactly what fish (1 species) you would like to try first, then research to find out what conditions are required to be successful and if you are able to supply those conditions, or able to buy the fish for that matter. You say you are short of time and money so your fish selection should keep this in mind. Discus will take more time as they require excellent water conditions all the time and plenty of water changes too. Good discus are not cheap and, if you want to breed fish, you should choose the best you can find, not the cheapest. I know when you first start you get all excited and enthusiastic but if you jump in over your head, things will not go to plan and you will get disillusioned and give up and we don't want that. We want you to enjoy the hobby for years to come! Something that is cheap to do, and easy since you live in Auckland with more constant higher summer temperatures, is to breed semi-tropical fish, like barbs, in a hard sided kiddie's swimming pool. I used to buy 6ft diameter ones from The Warehouse ($24.99 last time I bought one a few years ago) and set them up outside (in summer only as it is colder here in winter than where you are). Fill the pool with water and get a pile of oxygen weed from a local waterway somewhere (free). Add bunches to the pool and anchor each bunch with a rock. Once the temperature has warmed and stabilised at a minimum of 18C overnight, add the barbs and leave them to it. I have bred golden and Odessa and ruby barbs this way (not all at the same time in the same pool of course!) I don't want to put you off, and it is good to see such enthusiasm, but step back and have a good think about what you want to do and what is required to do it, then RESEARCH before doing anything else. Continue to ask questions here by all means but read books, search for information and consider joining the local fish club if there is one near you. Good luck