Hi J-J,
You're right, its very difficult to handle the overload of startup when you're new to this hobby and want to start a tank. It can be even more difficult in a sense when you stumble across an advanced hobbyist site like this and attempt to take it all in! But the alternative is worse! Lots of members here talk about "doing it wrong" for various amounts of time before they found TFF and usually say they wish they had found this place first. The most important thing of all is correct information, so that you can have a better idea about that hardware you're starting to list, and some patience and time here will head you in the right direction.
Take a look at an article written by my friend Miss Wiggle in the Beginners Resource Center. This is one of the articles that takes a stab at starting to address some of your questions. Perhaps even before that you should answer the question of whether the the hobby you seek, your emphasis in your first tank will be more toward tropical fish or more toward tropical plants. A larger proportion come first seeking to set up a fish tank and just perhaps want some nice plants in there too, but there are a few people who already know they are interested in the "planted tank" hobby, where 70% or more of the substrate is planted and growing plants is more the emphasis than the fish. If you fall into that minority category then it would be better to start our planted tank forum and then decide about equipment and startup techniques for that. Otherwise, if you fit in with the beginner majority, you are probably fine here, starting your homework in the Beginners Resource Center, with the article I mentioned (from here on I'll assume that...)
One of the easier bits of necessity you can seek even before a tank, surprisingly, is a water testing kit. This can give you a couple days to read the instructions in it and test your household tap water, well water or other source water. Regardless of what size tank, you'll need one. The important thing is to get a liquid-reagent based master kit and not the paper strip types of tests. Many of us like and use the API Freshwater Master Test Kit and you will see many members even using the test result colors as shorthand in discussions. The Salifert test kits are supposed to be even better and the Nutrafin kits are good too.
Meanwhile of course you should be taking into account what fish you want to keep, the water volume they would need and what your budget is and working toward deciding on a tank size. Larger tanks are easier to learn on for beginners. This is because a larger water volume is more forgiving of water chemistry mistakes and is slower to change. A small tank can turn deadly for fish faster than beginners can sometimes react to or figure out what to do about. Having said that, its obvious though that as tanks get quite large they become difficult in other practical ways! And expensive! So, personally, my own feeling is that there is a bit of a "sweet spot" in perhaps the 20 to 40 US gallon range, although 55G is quite common and would be really good too if you had the space, could afford it etc. 28 -33g I especially like but that may just be me. Many would say that 55 to 75 would be a great range!
What about the other hardware you mentioned? Well, it turns out that heaters are really quite trivial to figure out. They're necessary, but choosing one will be easy when you get to that stage. The basic guideline is 5 watts per US gallon as a rough guideline but they can be off from that some and still be ok, so just discuss it when you get close to the purchase. You'll want to get a simple glass thermometer with a suction cup to stick it to the side glass to use to set your heaters temperature and to monitor your tank temp.
In contrast to that, the filter is a whole different consideration. Filters are perhaps the single most core piece of equipment in the hobby and are the gear and the center of your focus as you learn the key first skills of fishless cycling and understanding the Nitrogen Cycle. The articles on the nitrogen cycle, the fishless cycle and the fish-in cycle are your first big homework assignments after that tank setup article I mentioned. The major types of freshwater filters are internal, hang-on-back(HOB), external cannister, wet-dries, and sumps. For the beginner, its almost entirely between the internal, HOB or external cannister. The functions of a filter are mechanical filtration, chemical filtration and biological filtration. There are special media (sponges, ceramic rings, ceramic gravels, carbon, polyfloss etc.) that each are better or worse at these various functions. I'm just listing all this so you can come back to this post and use it to ask questions and organize your thoughts later! Its important to learn enough about filter media to be able to know you are starting your tank with the right ones and not just something the store sold you.
There will be other things at startup too, substrate, tank cover, lighting, perhaps an airhose but I'm sure I've said enough now! The tropical fish hobby is all about slowing down and stepping out of life's fast lane. Enjoying your tank is a way to get away from the stress of work, traffic, computers, cellphones, people, all that stuff. It doesn't occur to people but the process of buying and setting up a new tank and learning can all be done in this new and different spirit of relaxing and being curious, rather than anxious, hurried and stressed! Anyway, good luck and welcome to TFF J-J!
~~waterdrop~~
