Ok that's progress!

tell me about sailing location (generally ie south Florida , great lakes etc) What type of sailing do you do now and have immediate plans for? Are you a day sailor now with dreams of a few trips or ?
My boat which is equipped as a coastal cruiser has instruments for wind direction and speed, depth and speed. The wind is helpful for sail trim but I'm old school and still mostly use the windex. The wind speed is nice so I can see if things are building and leave time to reef. Speed hasn't worked and I don't miss it but do have the parts to fix it. I choose not to hook the auto helm to the plotter because I don't ever want to become reliant on electronics. (personal preference). I force myself to keep my head in the game if you will.
My last boat had nothing and did fine. I had a handheld depth gauge. The only electronics on board were a radio and nav lights. It's all first what you can afford and second what you want.
If you are in an area where water is shallow or sandbars move I'd say depth is important. I'd have to sit down with google for sites but most instruments these days speak to each other using a common language (protocol) being NMEA 2000 and some use TacTic which is wireless but I can't say how proprietary it is. I'd have to look as I haven't worked with it. Basically you need to make sure all these items can speak to each other. You could have a Garmin plotter talking to Raymarine instruments with some third party auto helm. (Raymarine is all that comes to mind at 3 am!)
Another factor is how good are your eyes and do you have a budget? do you plan to do this in steps or one big bill?
I know full of questions but I am trying to narrow down your goals.
SC