@BrundlesGridWalk  I forgot to mention a couple of other things.  First, even you have an XPS 15 9560 model that includes a GeForce GPU, all display outputs are wired to the Intel GPU (the GeForce GPU when active uses NVIDIA Optimus to act as a render-only device that passes completed video frames to the Intel GPU for output to displays).  The reason that matters is that all Intel GPUs currently on the market are limited to three simultaneous independent displays, regardless of resolution, how they're connected, etc. -- so if you want to use three external displays, you'll have to disable the built-in display under Windows Display Settings before you can light up all three.  After you do this once, Windows should remember that configuration and automatically disable the built-in display whenever those three external displays are present.

And second, I forgot to mention one other option for connecting external displays, which even allows you to exceed the GPU maximum display limits.  That option is DisplayLink adapters, or docks that use DisplayLink for video (like the Dell D6000).  DisplayLink adapters plug into a USB-A port ("regular USB") and give you a DisplayPort, HDMI, DVI, or VGA output.  However, the reason DisplayLink-based solutions can avoid GPU restrictions is because displays attached through such adapters/docks are not driven directly by the GPU, which introduces a lot of drawbacks.  If you're curious, I did a detailed write-up about that in this thread, specifically the post marked as the answer, but the bottom line is that even if you come across that option in your research, I wouldn't recommend it unless you're confident that those drawbacks won't create a problem for how you intend to use those external displays.

For those type of "mini-dock" adapters, even if they have multiple display outputs, they typically only support using one at a time (like the Dell DA300), or if they allow using multiple outputs, they'll only mirror content across the attached displays rather than allowing you to use them as independent displays, i.e. extend mode.  The reason is that those adapters don't support DisplayPort MST.

Part of the reason the Dell docks are expensive is because they come with power adapters that allow them to charge the attached system.  If you want that capability on your XPS 15, your only options will be Dell docks because the XPS 15 requires a 130W power source for proper operation, which is above the 100W max of the official USB Power Delivery spec -- and most docks on the market don't even deliver that much, typically offering only 87W, 60W, or none at all.  If you connect your system to an undersized power source, you will typically experience performance throttling as the system tries to operate within the limits of the lower power capacity.  The only docks that will properly charge the XPS 15 models are the WD15 with a 180W AC adapter and the TB16 with a 240W adapter, both of which will provide up to 130W to the attached system because Dell is doing something proprietary there.  I mention the adapter capacities because both of those docks are also available with a lower wattage option (130W for the WD15 and 180W for the TB16), but those will not be sufficient when using an XPS 15.  The main difference between the two dock models is display bandwidth.  The WD15 can only handle dual displays up to 1920x1200 or a single display up to 2560x1600 (or 4K but only at 30 Hz rather than the default 60), whereas the TB16 can handle dual displays up to 4K 60 Hz or some triple display configurations because the fact that it uses Thunderbolt 3 gives it access to 4x as much display bandwidth.  Triple 1080p would work fine on a TB16, but not a WD15.  Incidentally, the same display bandwidth limit that exists on the WD15 would also exist on any "mini-dock" that offered both video output and functionality that required USB data, even if it DID support multiple independent displays.  I wrote a detailed post about USB-C operating modes here if you're curious.

If you don't care about being able to charge the system, i.e. you'd keep the system's AC adapter directly connected via the built-in jack, you could get a 3-port USB-C MST hub like this one, which has a version offering HDMI outputs or DisplayPort outputs.  That will give you enough bandwidth to run three 1080p displays (since that device would dedicate all USB-C high speed lanes to video traffic rather than allocating anything for USB data like a mini-dock), but obviously it only handles video.  Otherwise, you could of course run two displays out of some dock or adapter and then connect one of them to the system's built-in HDMI port.

Do you know if I could just use a USB-C to HDMI and then run one HDMI to the regular port? Will I be able to run them as two different displays that way (extended mode)? I will just use my laptop screen as the third in this case since you said the GPU can only run up to 3 anyway.