Here's my recommendation for getting started. The basic budget is $700, with a few options bringing it up to $1000 or so. For many new photographers, that might be sticker shock, but it's cheap in the world of studio gear. And, this is all stuff which can last a long time, even as your photography grows — and, it's completely brand neutral, so even if you decide to switch camera systems in the future, it can stay with you.
I don't know if $700 will "break the bank" for you, but figure that this is in the same range as a nice lens, and under the price of many, yet it opens up a door to a whole new area of photography in a way beyond what the purchase of a lens usually does.
I'm going to link to purchase pages from camera retailer Adorama. I'm not affiliated with them, and you can get all of this stuff elsewhere (Amazon, B&H), but Adorama happens to sell the flashes I'm recommending under their own house brand, which is nice. (They're also one of the handful of very reputable online camera gear stores.)
So, first: the Westcott Rapid Box Kit.

This includes two softboxes, one a narrow rectangle and the other a larger octagon. That's enough to get you started with a lot of the techniques in our lighting-basics series. It also comes with two light stands, which are pretty flimsy, but serviceable. So, this kit, $400.
You can get cheaper softboxes, but these are really easy to set up, well made, and nicely portable. They're small, which means you need to get them close — not necessarily a bad thing (or hard!) for indoor amateur portraits.
These softboxes are made for hotshoe flashes, so that's the next thing. I highly recommend the Godox V850 flash. This is a cheap but powerful all-manual flash, with two notable features. First, it uses a lithium battery for quick recharge time and in order to get hundreds of flashes without recharging. This is pretty cool (although of course can actually be a downside if you forget to charge — you can't just run to the corner store and pick up some fresh AAs). More importantly, they have a cheap option for add-on radio control, which lets you set power levels from the camera.
If you're in the US, the Flashpoint brand from Adorama is a good choice — they call it the Flashpoint ZoomLion. Otherwise, you can get Godox V850, Neewer TT850, or Cheetahlight V850 — all exactly identical (and interchangeable, except for where you get service from).

You'll want two of these, of course, so: $200.
You also need to add a transmitter and receiver set

plus a receiver for each additional flash. For the two flashes, that's another $100.
You can get more sophisticated radio control systems. These generally cost a lot more. They'll have advantages, like being able to be used with other brands of flashes, better range, and possibly better reliability (although I've had zero problems with that). And, you can get remote flash systems which offer automatic "TTL" exposure control. You don't really need that — and arguably, you don't even want it. The lighting conditions in your setup won't be changing rapidly as they might out in nature or moving around, and the camera's guess as to how light is going to fall in three dimensions is just plain going to be naive. It's better to set the values yourself. The nice thing about this setup is that you can do that from the camera — no need to go fiddle with each flash individually to change the levels. (You can have 16 different groups with different power levels, by the way).
So, that's the basic $700 setup. If you can go all the way to $1000, I'd recommend also adding:
- An extra flash battery — $50
- 2× Frio cold shoe adapters — $25 (see review on this site here)
- Another flash and receiver (for highlights, hair, getting pure white backgrounds, etc.) $130, or $142 if you add another Frio adapter
- A bigger, sturdier 9' light stand — $60. (Or go even better yet.)
- A 5-in-1 circular reflector — a small 22" disc reflector goes well with this kit ($20), but you could also go up to the 32" size ($30) — or get both. Bigger than that is useful too, but in my experience mostly only when you have a human being to hold it — it's unwieldy otherwise.
- A big roll of Gaffer's tape. ($25) Once you start using this, you'll wonder why anyone bothers with duct tape (or duck tape) for anything except actual ducts (or ducks).
That'll bring you to around $1000. A bunch of clamps, clips, and related accessories would be nice too, but I'd wait to buy those till you see what you want to hold where. And a dark backdrop is helpful too, especially if you're in a small space. (In a large space, you don't need a backdrop for pure black backgrounds.)