Need? Compass, a set of charts, and a radio. We were out on Ontario with one of our previous boats minus the radio (when I was in my 20's and stupid, and the weather turned crappy). Not recommended. If I had a radio that day, I might have listened to the weather channel, and not been out on the lake in the first place. These days, we have a radio on the boat and a hand-held backup.
Our current boat has a chartplotter. Now I think that's indispensable. I also use my 7" tablet with Navionics on it, as a backup, and for planning. Also indispensable. I still carry a chart book of the area we're in. Some of the new radios have AIS built in. That could be useful on Ontario. We also have a wheel pilot. It came with the boat. I never would have bought one. The wheel pilot broke, for good, a couple of weeks ago. Now it's indispensable. I just ordered a replacement. FWIW, Defender has the newest Raymarine unit on sale right now.
So, the bottom line is what you don't have, you may not miss, but there's a lot of cool stuff out there that can be helpful. Most of it isn't necessary, though, for where you are cruising. You also don't need to spend a fortune for some of these things. Handheld gps, or maybe a Navionics program on a tablet you already have, cheap fishfinder for depth, cruising guide and chartbook for the area you're cruising, compass, handheld radio, etc. You can make a set of telltales for the shrouds using yarn or tape from an old cassette. If your boat has a tiller, a Davis tiller tamer isn't the same thing as an autopilot, but it's the next best thing. You can start small and add things as you feel you need them.