I have an Inseego Mifi 8000 instead of the M2000, but the concept should be the same.
In order to get decent internet I have a rather complicated setup, but you can take the parts that work for you.
A drawing of my setup is here: https://imgur.com/0YeBOpE
This is the cell booster I bought in 2018:
https://www.weboost.com/products/connect-4g
This is the newer version of my cell booster:
https://www.weboost.com/products/home-multiroom
I use the GL-MT330N-V2 in bridge mode, which basically converts the wifi from the Mifi 8000 to ethernet.
The GL-MT330N-V2 I bought is here:
https://www.amazon.com/gp/product/B073TSK26W/ref=ppx_yo_dt_b_asin_image_o03_s00?ie=UTF8&psc=1
That ethernet is then used as the WAN for the ASUS RT-AC68U.
https://www.amazon.com/ASUS-Dual-Band-AiMesh-Router-AC1900/dp/B00FB45SI4
I have a second ASUS RT-AC68U in a remote building and they are connected via AiMesh.
The key here for your situation is that since the Mifi 8000 and GLi.net are connected via wifi, the USB on the Mifi 8000 is then plugged into a standard lamp timer to make it run on battery for 6 hours then charge for 6 hours.
Hopefully this is more helpful than confusing.
I would recommend a wireless AC router at minimum.. something with decent range. One of the best routers out now is the Asus RT-AC5300 Pretty pricey, but does a hell of a job.
What I currently use is the RT-AC68U. No router's aren't going to be cheap, no matter how you look at it. However going with at least an AC router prepares you for future internet upgrades. If you really want to get prepared for whatever comes down the road years from now.. Look into a Wireless AD router. Not many out currently. I think TP-Link has the first and only one out at the moment.
Depending on your speed you are paying for. The SB6183 modem would be just fine in most cases.