You can do basically all of the features without having the gateway kit, the only difference is you must do them from the remote instead of the GPS unit.
I fished for 1 full season with my xi5 before getting the gateway kit last year. A couple reasons 1) it wasn’t out yet 2) I had Gen 1 HDS units so it didn’t work with those anyway.
Last year I upgraded one of my dash units and installed the gateway. I have the xi5 sonar cable hooked to an old Gen 1 unit, but the gateway network is connected to a unit at my dash.
Without using the gateway you can still record routes, set anchor points, use autopilot with cruise control all of the native features, but what you would gain by have it gateway connected would be to navigate “to” a location that is on your GPS unit. You could also select a point on the GPS and have it “anchor here”. By not having the gateway you just have to arrive at your destination and then anchor mode. The gateway will also allow you to set your speed on the GPS unit, vs using the remote. The remote is fine, just remember when you initialize cruise the speed is 1.0MPH. press the + or – to change the speed in .1MPH increments.
Not a big deal and you will still really enjoy the features by not having the gateway.