>>15066568
Soft pads won't cut it, honestly. They're only fit for very basic entry difficulties.
3k will hardly get you a full arcade machine unless it's missing important parts. But it's more than enough money to get yourself a nice hard dance platform like the ones from Precision Dance Pads. With that, connect via USB, launch StepMania and play whatever you want.
With leftover money, consider the option of building your own custom arcade-like cabinet, if you have some wood and metalworking skills (or know someone who does). Get a mini tower for the internal PC, hook it up to a nice TV/monitor, and install a good pair of speakers.
Optionally you could do light decorations similar to how the FX model of Pump does, by having the audio output drive a VU meter light show, or something along those lines.
And with a setup like this, there's no need to limit yourself to DDR/PIU/ITG/etc, you could build custom controllers fit for your cabinet featuring basic stick + buttons for arcade games, or specialized controllers for stuff like Pop'n, other Bemani games or even Bishi Bashi.
The base for any custom arcade controller can be something fully featured and ready-to-use like an iPac (https://www.ultimarc.com/ipac1.html) or you can just grab one of these cheap $10~ USB gamepads (snes style, PS1 digital style, PS2 style), take out the board, put it in a plastic box, then solder wires to each button you'll need along with the ground for each one.
The latter is something I'm working on and got most parts for. I have a custom built PIU pad that I fitted with the guts of a PS1-like USB gamepad, soldering wires directly to the exposed contact points on the board. But said board is in the middle of the top two (Red) arrows, so I'm worried I might end up damaging during play. Therefore, I'm envisioning making a generic control box that'll house the USB gamepad board with its regular USB cable sticking out from one side, and a DB-15 (VGA) connector on the other. From there, I plan to install another DB-15 on the side of the PIU platform and then solder the cables to that. Then I can just use a regular monitor cable to combine the two and have a go. This allows multiple controllers using the same box (as long as they fit under the limits of the DB-15 connector, which would be enough for most controllers). "Before and After" in the hastily drawn pic related, e.g. with a regular controller box with stick+buttons, PIU pad, and Pop'n (or Bishi Bashi!) controller box.
Having an original dance machine is neat too, but that comes with its own drawbacks. e-Amusement machines in general means you probably will lose some content as the system is a bitch to work with, and you can't just stick custom songs like in Stepmania. It's still a more 'original' experience, though. But again, 3k will probably not be enough to get a decently functioning machine…