Betta Care: My Standard Setup (& Price Breakdown)

There's a lot of different environments that you can keep a betta fish in. 

However, when I'm setting up a new environment for a fish, here's what I get:

TANK: 2.5 or 5 or 10 gallon rectangular tank with lid.
What one I get is usually based on how much space I have to put it. 
Circular and bow-front and other tanks take up more space for the same water volume. Since I have a lot of fish, I rarely have a lot of space to put a new fish tank.
Another consideration is weight. A 2.5gal tank, set up for betta, weighs about 35 pounds. A 10gal tank, set up for betta, weighs about 115 pounds. Make sure your furniture and your floor is ready

(it's that little black thing in the back)

HEATER: In general, I like glass heaters. I'll use paddle heaters for 2.5's. I use up to 10w/gallon (25 watt heater for a 2.5, 50 watt heater for a 5gal) as a guide for maximum heater size.
If it's a submersible heater, I like to put it horizontally by the floor. This lets me drain most of the water without unplugging my tank.

THERMOMETER: If you have a heater, you need a thermometer. I use glass thermometers because they're more accurate than the kind that stick onto the outside of the glass. I prefer sinking thermometers to floating thermometers, but both work. I don't like that floating thermometers tend to free themselves from the wall and run around the tank without you. Here, I've got a magnetic horizontal thermometer, which I really don't like.

 Right, sponge, left, filter

FILTER: For a 5gal tank, I almost always use sponge filters. A sponge filter also needs a air pump and airline tubing with it. I use black silicone airline tubing because I like how it looks. I've also had luck with Tetra's HOB for 5gal tanks
For a 10gal, I either use a HOB filter or two sponge filters.
For a 2.5, I use either a sponge filter and a throttled air pump, or I leave the tank unfiltered if I know I will be able to ALWAYS stay on top of my water changes.
I don't like internal power filters. I've never had bad luck with them, but the idea of having all the electricals INSIDE the tank with my fish always makes me nervous.

Tank, heater, thermometer, filter. If you have a betta fish, your environment needs to have those four things. There is no good reason to not have those four things. They're the bare minimum.

Now, the things you put in it:

Substrate: I like gravel. I tend to have gravel on hand in case I need to set up a tank on the fly, or in case I change my mind about how I want a tank to look. Enough gravel for the bottom of a tank weighs less than enough sand.
You don't need substrate, but I think it looks nice. 

Cave: Your fish needs somewhere to hide. You can buy cool looking caves at the pet store, or you can use a flowerpot or mug on its side. Make sure it has no metallic decoration or paint that would flake off. If it's got a hole big enough for the betta to put his head in, plug it with some hot glue or something, because they can and will get stuck.

Plants: I like silk ones, because I think they tend to be prettier.
I've found that I like the look of heavily-decorated tanks better than sparse ones. I like having at least two plants that are as tall as the tank itself, and then shorter ones for the front. 
I like having plants to cover up where the sponge filter will be, so I don't need to look at it. I've also found that having tall leaves near the surface helps break up the bubbles from the sponge filter

Other: Once you have the tank, filter, heater, thermometer, cave, and enough plants to make the fish feel safe, everything else becomes about what you want. There are people out there who will talk your ear off about human amusement vs fish needs, but I don't think applies here. 
A legitimate comment about putting human amusement above fish needs is if you wanted to keep a fish in a wine glass, or wanted to use fish as decoration for a party. There, you've taken the needs of the fish, and said you don't care about the needs of the fish, because you want to put the fish in a wine glass.
However, when you've made sure you have already met the needs of the fish, and you are making sure that nothing you are doing is harming the fish, there's nothing wrong with setting up a fish tank that you really enjoy looking at. If you want an ornament that looks like Spongebob, or you want a tank backdrop, or you want whatever you think looks cool, feel free to add it. It is not wrong to want your fish tank to make you happy, as long as your happiness is not coming at the expense of the fish's health.
If you run into someone ready to lecture you on that who DOESN'T keep their fish in opaque sterilite bins, send them to me because I'd LOVE to call someone on that kind of hipocracy.

Price Breakdown of my ideal betta setup:
$16 -- Tank (2.5 with lid, Great Choice brand, at both Petsmart and Petco) or
($10 for a 10gal)
$16 -- Heater (Great Choice 15w paddle, Aquaeon 10w Mini) OR
($30 -- Heater) (Marina 25w, Aquaeon 50w, Tetra 50w non-adjustable--for larger tanks)
$3 -- Thermometer (any brand, as long as it's a glass internal thermometer, should run you this price range)
$9 -- Air Pump (the smallest one you can stand the sound of)
$3 -- Airline Tubing
$6 -- Sponge Filter
$4 -- Gravel
$1 -- Flowerpot Cave
$7 -- Plants (Petco has a silk plant set that has 3 small and 3 tiny plants, which would be great for a 2.5, and they have a set that is 3 medium and 3 small plants that'd be a great start for decorating a 5 or 10
Puts you at  $65 for my ideal 2.5 or 5 gal tanks and $73 for a larger. 

Note this is just enclosure and living space. Tack on another
$5 for Seachem Prime, $8 for Omega One, $3 for a fish bucket and $10 for a decent siphon and $6 for a good power strip to plug it all into. 

My analysis here comes up to, if you know you're going to get a betta fish, set aside around $100 to do it with. 

Most of us don't plan on getting betta fish before we do. We fall in love with one at the store, a friend is getting rid of theirs, you rescued it from being thrown away after being used as a party decoration...

In my case,

It has been

260 0

days

since the last betta fish impulse buy incident

What I've noticed is that, unless you have a big stash of fish-related things hanging around (like I do), it's almost always cheaper to buy all of the things for the fish, and then to buy the fish. This gives you a chance to go price shopping and buy things you need online. 

You might shrug off a lot of things as, "I don't really need that," when you first get the fish, but be aware that you'll end up spending that money anyway, if you want a healthy fish.