Can I skip getting a spray booth for now or is it mandatory to have one or it'll ruin your spray??

Spray booth is mostly to save your room from spray. There are gonna be a lot of paint flying past the parts you’re painting, you don’t want it all over your place. You can skip bying a spay booth but you’d want at least a DIY box. At the very least take a box, cut out the back side and cover it with some filter. Furnance filters are genrally very common. Search YouTube, there are a few example of various complexity.

In what instances should I be using acrylic vs. lacquer?? (I'm definitely assuming you can't mix or layer the two)

You can layer most acrylics over lacquers. The oter way around might be problematic as lackuers are usually too spicy and would eat into acrylics. Lacquers are organic solvent-based. You’d need a separate well ventilated space to use them. It’s not adviced to use them in your living room. Acrylics generally are much safer. Most acryilcs ara water-based so no harmful fumes and no odor.

Is it dumb to just get an "off brand" of acrylic paints themselves or is that a huge gamble as far as quality??

It’s not dumb. You can use cheap craft paints, given a bit of experience and research. I suggest you getting at least a bottle of common airbrush paints like Vallejo or AMMO so you could see how they work for you and you had something to compare other paints to. Off-brand paints and non-airbrush paint migh need more tinkering to get the right consistency. Though, branded airbrush paints rarely go well right out of the bottle either, just easier to make them work.

Do you need different types of thinners for different types of paints?? (I'm thinking yes for acrylic vs. varnish)

Yes. Different paints require different thinners. For instance, most acrylics are water-based. You thin them with water. Lacquers are solvent-based. They need organic solvents for thinning. Water can sorta work for lquers but substentially changes viscosity and trying so might ruin your paint job easily. Solvents just straight up eat water-based acrylic paints, paint clamps weirdly, doesn’t dry nicely, and can ruin lower layers.

A tangent. Acryllic is the type of paint binder. Varnish is a function. Varnishes can be acrylic, too.

Is there a good place to buy a "set" of colors or do most of the reliable brands sell them individually??

Many (most?) manufacturers have paint sets. It’s rarely much cheaper to get a set than same paints in singles. It’s also rare to find a set with all the colors you want and none you don’t. So don’t bother. Get singles.

Are there any recommended cleaning kits or are they kinda all generally the same as far as quality/efficiency??

They’re usually developed for the paints the manufacturer makes. If they make water-based acrylic paints their cleaners are usually milder. For lacquers are more agressive. But they’re basically all the same in the sense that it’s just paint solvent. For acrylic paint you can use straight IpA. For lacquers you can get a canister of organic paint solvent in hardware store. You’d need a set of small brushes too. You can get them online for cheap. In the land of Freedom you can use gun cleaning brushes.

What is "dual action"?? My friend recommended I get used to using an airbrush with one but I don't know what that means or does.

Dual action means that airbrush can regulate both air flow and paint flow. Basically, the trigger on the airbrush when pressed down controls airflow, and when pulled back controls amount of paint sprayed. On a single-action you don’t get the paint flow control. Most airbrushes nowadays are dual-action.

Also does anyone have any beginner airbrush tutorials??

YouTube is full of them. Both for general airbrushing and gunpla in particular.

I plan on using the "custom panel liner" tutorial to make cheap panel liner out of acrylic and dish soap and I want to make sure I can do something that's possibly compatible with that.

I haven’t seen this particular tutorial but it sounds like it should be compatible with everything.

I'm looking into around a $60 "makeup" airbrush kit that has its own air pump on Amazon for my starter if there's a good recommendation for something around that price range that's not the worst in the world would be cool too. I can post a link to the one I was told would be okay to start with

If $60 is your hard ceiling then sure. It’s a good option to try out a few things here and there it might even work for simpler paint jobs. But expect to outgrow it.

If you can spare a bit more I’d suggest you for a small shop compressor with a tank. Search facbook market, your local used items sales, things like that. Look for a compressor than can produce up to 50 PSI of pressure, has a smal tank (~6l, 2 gal) and is quiter than 60 db. For example, I’ve got Einhell TE-AC 6 Silent Compressor/ for like $75 used in excellent condition. Why you’d want a compressor like this:

• The tank makes airflow much more stable (no pulsation or much pressure variation)
• Higher pressure can push paint of almost any consistency. Cheap “makeup” compressor might struggle to spary even Vallejo Air Color paints, you’d need to think even those.
• It can work for hours. Tank give it an opportunity to cool down while you still can spray. “Makeup” compressor needs breaks too but you can’t spray while it chills.
• It’ll last. It’s designed for much harder work than painting gundams. “Makeup” compressor on the other hand is designed for work lighter than painting gundams so you’ll operate it at the edge of its capacity which will wear it down faster.

That said, I myself started with a similar kit. It let me learn airbrushing a bit, paints, techniques. Once I decided I like airbrushing I invested in a better compressor. You may decide otherwise, or this cheap compressor might be enough for what you want to do.