Inspiron 5559 Docking Station

The D3100 has poor reviews because it does not charge the attached system (which many people incorrectly assumed it would since it's called a "docking station") and it uses a DisplayLink chip to drive attached displays. With DisplayLink, displays are not actually driven by the system's GPU. Instead, the system's CPU and GPU compress rendered display data for transmission as standard USB data, and the DisplayLink chip in the dock then decompresses it before sending it to the displays. This allows displays to be attached over regular USB (rather than just USB-C, which actually does have a native GPU output wired to it), but the compression and transmission as regular USB traffic can have some adverse side effects. For example, when large portions of the display area change at once, such as when watching full screen video or gaming, the display can appear to bog down and/or show compression artifacts. This can also occur during periods of high USB activity from other devices (e.g. sustained transfers to/from an external hard drive), which forces display data to compete for USB bandwidth, and during periods of high CPU utilization, which leaves less CPU capacity to compress the display data for transmission over USB.  Lastly, DisplayLink also increases It CPU and GPU utilization overall, which means less performance available for other tasks and faster battery consumption, although the latter admittedly isn't an issue with dock-based implementations of DisplayLink.

So if all you'll be using these external displays for is spreadsheets and email, the D3100 may be fine, but otherwise, you may not have a great experience. Unfortunately, since your current system doesn't even have a DisplayPort output, multiple external displays driven natively by your GPU isn't an option.  If you had DisplayPort, you could have used daisy-chaining or an MST hub for displays, but that wouldn't have gotten you peripheral connectivity.  However, if upgrading the laptop is an option for you, then get a system that has either USB-C or (best of all) Thunderbolt 3, since the latter gives you everything from USB-C plus the extra capabilities of Thunderbolt 3.  That would allow you to use a dock like the WD15, which would get you 2x 1080p displays, or if you got a system with Thunderbolt 3, you could instead use the TB16, which would allow 2x 4K displays -- and with both of those docks, the displays will be driven natively by the GPU, not through a DisplayLink interface.

Just make sure that your BIOS, drivers, and (if applicable) Thunderbolt firmware and software are all up to date.  Both of those docks had a pretty rough introduction because it took a while for all of that software and firmware to stabilize.  The Thunderbolt dock was actually originally called the TB15 and had to be recalled in favor of the TB16.  The good news is that things actually work now, lol -- except for a recent string of BIOS updates for certain systems that created unstable USB connections on the TB16, but the BIOS updates to fix THAT have already started rolling out.