Welcome to TFK! You'll find a great bunch of folks here (just ignore the few crazy people
I agree with others....get the biggest tank you can afford that will fit nicely where you'll keep it. Bigger tanks are more forgiving and easier to manage.
You'll need a stand, hood(s) w/lights, a heater and filter as basic equipment. You will also need substrate, plants and fish.
You just might find a good deal on an ensemble which is stand, tank on hoods/lights.
Heater - For the heater there are many. I use a couple of Aqueon Pro heaters. I like them because they have green/red indicator lights and instead of glass, they are plastic covered aluminum - nearly indestructible. I use two, although each has sufficient wattage to maintain the tank at room temperature. This gives a redundancy if one was to fail or the room temperature was to drop significantly.
Filter - I'm a fan of Aquaclear HOB (Hang On Back) filters as unlike cartridge filters, we can control the type and volume of filter media. (Mine right now just use sponge material. If you get a large tank (55g or more) you might want to consider a canister filter. There are many to choose from but the top three brands seem to be Eheim, Rena, and Fluval.
Substrate - Gravel or sand. For s zillion years, I always used gravel....sometimes even with under gravel filters. Nowadays, I use (pool filter) sand and like it much better because uneaten food and detritus (plant and fish waste) stays on top instead of settling into the gravel.
PLANTS - Living plants (even if you just use floating plants) offer a huge advantage in water purification, supplemental food and resting/hiding places for fish.
(shhh...I cheat and have plastic 'rooted plants' with lots of living, floating Anacharis plants.)
For some rooted plants, you may need more powerful lighting. In any case, you want bulbs in your lights that produce 6500k lumins.
Fish - I can't recommend specific species as everyone is uniquely drawn somehow to particular fish. HOWEVER, I can recommend that you use this boards 'TROPICAL FISH PROFILES' (top of forum page) to ensure you select the correct species quantity and mix.
Don't get many fish at first, just a couple. You'll need to (nitrogen) cycle tank which is easily done if you have plants, but still better done with just a few fish to begin with. (The cycle is the conversion of ammonia to nitrites and nitrites to nitrates which you should read up on in the articles section).
So there is the tip of the iceberg in tropical fish keeping. Of course you should have a test kit for testing water parameters (API Freshwater Test Kit is preferred) and you should do weekly water changes so you will need a gravel siphon or hose and buckets or a Python like hose device that hooks to your sink. If you have chlorinated water, you will need a conditioner to remove the chlorine. There are many, but I like Seachem Prime.
Okay, that's the basics off the top of my head. Hope it helps in some small way. Keep us posted of your progress and again, welcome to the forums.