Wow, Jonas, most of us experienced our first fishkeeping disaster AFTER we set up our tank!
I was all geared up to give you some great stocking advice for a 55 gallon, then I read about the wreck. Wow. Glad everyone is OK.
I agree that you're getting a lot of very sound advice, some of it very complicated stuff that you really don't need yet. It's possible to keep it fairly simple. Here's what I think:
First, settle on a tank size. 20 long, 36g, and 55g are all great tank sizes with many possibilities. So no problem there. Just decide what you like and what you can afford. Any could work for a dwarf gourami; with a 55 you could get a group of pearl gouramis!
Second, if you haven't, figure out your water hardness. That will affect what fish will thrive in your area. You can either get a hardness kit from your pet store, or just call your water company and ask them. If you already did this, I missed it, so please enlighten me.
Once you figure that stuff out, we can go from there.
A few other hopefully comforting thoughts:
1. Filtration doesn't have to be that complicated. Once you pick out a tank we can help you with that. For a beginner, I'd recommend a simple hang-on-back filter, rated for twice your chosen tank size. Super easy to set up and maintain. You can tweak the filter media and all that later, but a cheapo HOB will get you started.
2. Plants are not that complicated, and in the long run make fish keeping easier because they make your fish happier. Just make sure you get an adequate light. Again, we can help you with that once you decide on a tank.
3. I agree completely that play sand or pool filter sand are great substrates. Dirt cheap, too.
4. Most important, remember that this is supposed to be fun! One thing at a time; don't get overwhelmed by the details. If you're getting stressed about it, you're doing it wrong.