I'm planning on doing a ArduPilot boat

I’m also planning on connecting it to Pi4 and make the boat connection 4G.

I’m planning on doing boat with 2 propeller and 2 rudder. (I’ve 3d Printer so I can print this parts)

I’m really noob and don’t know where to start and what should I buy to make it work. ( For now I only have Pi4.

If Anyone can help me it would make me really happy